That concludes today's updates coverage of the Christchurch earthquake. We'll be back in a few hours to resume updates from around 6.00am. Thanks.
Newstalk ZB has confirmed a woman rang the radio network's overnight host and said her 9 month old grandson was killed when the television fell on him.
Shirley Wan felt the earthquake in Dunedin. "I am in Dunedin. When the earthquake struck i was on the 8th floor of our building and it swayed heavily for atleast 10 sec. At that point I knew Christchurch must have been hit hard."
Another eyewitness account.
Denise Biddick emailed nzherald.co.nz to say: "I was in Mt Pleasant. It was absolutely terrifying. We sheltered under the table which moved around a lot. Everything in every cupboard fell out, the drawers, the wardrobe, the shower door, sell off and over. Two windows broke, french doors fly open with broken windows. I had experienced the previous earthquake, this one was much more extreme. I knew immediately that there would be deaths. I waited three hours before driving home to Cracroft. The devastation as I drove down the hill was enormous. Houses with the whole front missing. People milling out on the street in shock. Roads with tarmack lifted, water running everywhere. It was huge. Much much worse than September."
Eyewitness, Fiona Stead, provided nzherald this account.
"I work in Sydenham. Was just going back inside prior to starting work again on the 1st floor of our 4 floor building when the quake struck. Myself and a colleague ended up on the floor, unable to stand, due to the quake.
"Building was evacuated. Air Conditioning unit on top of building erupted, water everywhere. Broken windows, people injured from failing ceilings on the 4th floor. Damage so much worse than intial September quake.
"Seriously scary. Have never been in anything so scary. Was sent home. Leaving to go to my car, people lying on Colombo Street - injured. A work colleague said Westpac Helicopter took them to hospital due to congested roads. Sydenham district has been badly hit again - buildings partly damaged last time, have come right down this time."
A Christchurch eyewitness provided this chilling email to nzherald.co.nz: "I work at Ballantynes, it was chaos! Buildings were falling down everywhere. When evacuating, a little girl about 7 was being carried towards the river, lifeless with rubble all over her. Another man lay impaled by a shop front.
"I was getting very frustrated with people taking photos when others where trying to reach a safer place. My heart goes to those who are currently trapped."
This timelapse map shows yesterday's quake and aftershocks as dots. For the most impressive results, change the time to 'last 24 hours'.
The Guardian is running a live blog of events here.
Its Tokyo correspondent Justin McCurry filed on the Japanese students thought trapped in the collapsed CTV building.
"The 23 students from Toyama college of foreign languages were eating lunch at King's Education, a language school in Christchurch, when the quake struck. The school is reportedly located inside Christchurch's CTV building, which collapsed in the earthquake.
"The students, 12 of whom are still unaccounted for, arrived in the city last week and were due to study English in New Zealand until 13 March.
"Japanese media are reporting that a student and graduate of a language school in Kyoto, as well as three female students from Kagawa University, have not been heard from since the earthquake."
Queen Elizabeth II said in a statement she had been "utterly shocked" by the news.
"My thoughts are with all those who have been affected by this dreadful event," the statement, reported on the BBC website, said.
A Facebook page has been set up to find offers of free accommodation for those left homeless by the quake.
Within the next 24 hours 50 officers from the Wellington police district, including two disaster victim identification officers and two recovery dogs, will travel by ferry and road to Christchurch, police said in a statement.
Twenty officers from each of the Tasman and Southern districts are driving overnight to Christchurch and a further 43 Southern district staff will travel tomorrow morning.
Thirty officers, including six disaster victim identification staff and two recovery dogs, are travelling from the wider Auckland districts tomorrow.
Another 130 staff are being drawn from other police districts over the next few days as part of the second phase of police reinforcements.
A Royal New Air Force Boeing 757 is heading to Christchurch from Whenuapai Air Force Base in Auckland carrying 54 Urban Search and Rescue (USAR) staff, 20 St John staff, and a staff member from Customs.
It picked up a further 34 USAR passengers at Ohakea and there were also two sniffer dogs on the flight.
Two Iroquois helicopters from Ohakea have also arrived to assist with rescue efforts in the city and a P-3K Orion aircraft is taking aerial surveillance images of affected areas.
The Royal New Zealand Navy's multi-role vessel Canterbury is in Lyttelton and has offloaded about 160 personnel for cordon support duties.
HMNZS Resolution has completed a survey of the main shipping route into Lyttelton harbour and results passed to port authorities.
HMNZS Otago is en route to Lyttelton. HMNZS Pukaki is at anchor with an element of the navy dive team.
More than a thousand Christchurch residents have nowhere to sleep tonight.
The Salvation Army's Major Robert Ross says workers are gearing up to help people who have been displaced. "It looks like in excess of 1000 people will require assistance tonight," he told Newstalk ZB.
Major Ross says while that was initially going to take place in Hagley Park, operations have been moved to Burwood.
Australian Prime Minister Julia Gillard says many Australians have called an emergency hotline, concerned about loved ones caught up in events in Christchurch.
"Already that line has taken 2,541 calls and it has registered 443 cases of Australians who are in Christchurch," she said.
About half of Christchurch remains without power following today's magnitude 6.3 quake, and lines company Orion Energy is warning it will take several days to make repairs.
Up to 80 percent of customers lost power when the quake hit just before 1pm and Orion had managed to restore it to some.
"We have found serious damage to both major cables and substations in the New Brighton and Dallington areas," Orion Energy chief executive Roger Sutton said.
"This is very substantial damage and it will take us two or three days establish a repair time," he said.
"We hope to get small pockets of these areas back on later tomorrow,but substantial repairs will take much longer."
The damage sustained was far more serious than any damage from the September 4 quake.
Damage throughout the area was more substantial, especially in the central city, Summer, Lyttelton and Heathcote areas.
"We have started to restore power back to areas west of Cathedral Square," Mr Sutton said.
``We now think we have 50 per cent of power back on to Canterbury (but) there are still substantial areas of the city where we have not been able to access the damage at this stage."
Orion's main building was largely undamaged, Mr Sutton said.
"I was in our building on the ground floor, and I managed to get under a table, and then I went out into the street and it was an extraordinarily terrible sight."
Routine elective surgery will be cancelled in Auckland tomorrow as staff prepare to treat people injured in today's devastating quake.
An injured woman and a child will be flown from Christchurch to Auckland for treatment once transfer times had been arranged, Auckland District Health Board (ADHB) said tonight.
The woman would be treated at Auckland Hospital, while the child would be treated at Starship Hospital.
ADHB incident controller Margaret Dotchin said Auckland had beds and capacity in its intensive care units to support Christchurch in its time of need.
Its incident management team was in regular contact with agencies coordinating the earthquake response.
Ms Dotchin said two intensive care nurses and three general nurses were on standby to be transferred to Christchurch. Several surgeons, anaesthetists and intensive care staff were also on standby.
Air New Zealand has reduced domestic airfares in and out of Christchurch to $50 for those who book before Friday.
The discounted tickets will be available to anyone in New Zealand through the carrier's website and call centre.
A return Auckland-Christchurch flight will also be available for $50 tomorrow, a statement says.
Air New Zealand CEO Rob Fyfe, who is in Christchurch, says Air New Zealand will regularly review capacity and compassionate fare requirements over the coming days.
He has offered the full resources of the airline to Christchurch Mayor Bob Parker and Prime Minister John Key.
Civil Defence and safety considerations are severely restricting the ability of Telecom network technicians to carry out physical work tonight.
But Telecom said it was continuing to monitor network capacity and performance, with a particular focus on 111 services and key emergency response sites.
"All central city cell sites that are operational have been connected to generators to keep them running overnight," the company said in a statement.
Telecom said the disruption to landline and mobile services in Christchurch was continuing.
Mobile performance had improved as people heeded calls to limit non-essential mobile use.
Vodafone said its mobile network continued to be fully operational, but due to the current demand on telecommunications we are experiencing some congestion.
Twelve Japanese students from a foreign language school have been reported missing in the rubble of a Christchurch building.
The Sankei Shimbun newspaper said two Japanese teachers and nine students were rescued, but 12 students from were missing in the Peterborough St building. They are from Toyama city.
NNN television news network has quoted Toyama city authorities as saying that three of the rescued students have been taken to hospital, one in a serious condition.
All schools and early childhood services in Christchurch City were closed until further notice tonight, the Ministry of Education announced.
Updated information would be posted on the ministry's website by 1pm tomorrow.
Governor-General Sir Anand Satyanand says he is shocked and distressed about today's deadly earthquake in Christchurch.
Prime Minister John Key tonight confirmed at least 65 people had died in the 6.3 magnitude quake which struck the South Island's largest city at 12.51pm today and the toll was expected to rise.
"Having just left Christchurch this morning it has been with great shock to learn of the latest earthquake to hit Canterbury this afternoon. I have been informed of damage, serious injuries and, most distressingly, significant loss of life," Sir Anand said.
Coming after last September's devastating quake, today's tremor would be traumatic to the people of the city and region who had endured six months of aftershocks while trying to put their lives together, he said.
"My wife Susan and I join all New Zealanders in our thoughts for the people of Christchurch and Canterbury at this terrible time."
Luxury cruise liner Queen Mary 2 will most likely cancel its visit to Christchurch, which has been devastated by a major earthquake.
The two Cunard liners Queen Mary 2 and Queen Elizabeth made maritime history when they passed each other for the first time in Sydney Harbour on Tuesday.
Queen Mary 2 was due to sail for New Zealand on Wednesday evening, calling in Christchurch on Saturday and Auckland on Monday.
"Queen Mary 2 is due to go down to Christchurch," Cunard director Peter Shanks told AAP on Tuesday.
"We're working with our team to make sure we do the appropriate and considerate thing.
"It seems very unlikely that we'll be calling in Christchurch.
"The people in Christchurch are clearly having a very traumatic experience."
Two more large aftershocks have hit severely damaged areas of Canterbury.
A magnitude 5 quake struck 12km deep and 10km south-east of Lyttelton at 7:43pm. It came on the heels of a 4.6 magnitude quake at a depth of 5km and within 5kms of the town at 7:28pm.
Christchurch Airport is to remain closed tonight to all but emergency and aid flights.
Airport spokeswoman Monique Oomen told NZPA the domestic and international terminals had both suffered some damage and needed to be checked before flights opened again.
"We hope that domestic flights can resume at 8am tomorrow, and we will send out confirmation of that at 6am," she said.
"International flights are cancelled until further notice, because there's a little more damage there. We hope they can resume tomorrow afternoon, but confirmation will be about midday.
"Until then, we ask that nobody comes to the terminal unless they get confirmation that it's open again. If it's closed, we won't be letting anybody in."
Another large aftershock has hit Canterbury.
The magnitude 4.6 quake hit 10km south-east of Lyttelton at 6:59pm. It was the third aftershock in the last hour.
A magnitude 4.3 aftershock struck at 6.03pm 10km south-east of Christchurch at a depth of 5km. A 3.9 magnitude aftershock struck at 6.17pm in a similar location at 15km deep.
Christchurch Hospital is bracing for a sudden increase in new babies as women go into premature labour as a result of today's massive earthquake.
The number of babies born spiked following the 7.1 magnitude quake last September 4 and a repeat is looking likely today.
A nurse told NZPA she had gone into work to help out because "last time everyone went into labour and it's happening again".
She had left her "trashed" home to help out.
There were reports of "chaos" in the intensive care unit, with "people everywhere".
Christchurch Civil Defence spokesman David Miller says information on the extent of the damage to Lyttelton is still "very scratchy" as roads into the town have been closed.
But he says it has been severely hit, with widespread structural damage and building collapses expected.
He says he does not know how many people had died in the small town or how many remain trapped under rubble.
There have been two further aftershocks in Christchurch since 6pm, GNS Science reports.
A magnitude 4.3 aftershock struck at 6.03pm 10km south-east of Christchurch at a depth of 5km. A 3.9 magnitude aftershock struck at 6.17pm in a similar location at 15km deep.
Christchurch Mayor Bob Parker says Hagley Park is no longer available as an evacuation centre; instead, those whose homes are not safe to go home to tonight and who need shelter are advised to head to Addington Raceway or Burnside High School.
The NZ Food and Grocery Council says suppliers are focusing on ensuring continuity of food and water supply to the people of Christchurch.
A number are expanding production outside of Christchurch to ensure basic staples are back on the shelf as soon as possible.
Christchurch Mayor Bob Parker says authorities are doing all they can but residents will have to help each other.
"We're in this together."
Prime Minister John Key tells TV3 the authorities will be working through the night to try to free those people still trapped under rubble.
Speaking from Christchurch after flying down this afternoon, Mr Key told One News it was likely the quake would prove to be New Zealand's "darkest day".
"It's just a scene of utter devastation, it's just so vastly different from the last earthquake where yes there were some horrifying scenes but this is central city at a very, very busy time where you've had a massive earthquake it's been violent shaking on probably what was very weakened infrastructure."
Mr Key said New Zealanders should be assure the Government was doing everything it could.
There were 180 police on the ground, a further 200 were on the way and 350 military were already in Christchurch with another 250 to arrive soon.
The Government had accepted offers of specialist help from Australia and US.
Prime Minister John Key tells media that as many as 65 people have died in the earthquake today.
GNS Science reports yet another aftershock this time a magnitude 4.0 at 5.56pm, measured 10km south-east of Christchurch. The 20th since the 6.3 earthquake at 12.51pm.
A 3.6 magnitude earthquake also struck at 5.29pm, 10km east of Christchurch, followed a minute later by a 3.5 quake within 5km of the city.
St John Ambulance says it received 53 calls, including 40 priority one calls in the two hours following the quake.
It advises people with minor injuries to stay at home, and those needing treatment to go to triage centres established for the injured at Latimer Square in the central city, Spotlight Mall in Sydenham and Sanitarium in Papanui.
Meridian Energy says its Christchurch-based customer call centre has been closed following the quake.
It says it is working hard to restore essential services for customers and hopes the call centre will be up and running for other parts of the country as soon as possible.
Further updates will be provided on the company's website meridianenergy.co.nz as they become available.
Civil Defence Director John Hamilton tells media the confirmed death toll stands at 17 so far.
ANZ announces it is donating $1 million in relief to victims of today's earthquake.
Its ANZ and National Bank branches have opened new appeal accounts to take public donations on behalf of the Canterbury Earthquake Appeal.
People can also make donations to the ANZ via online banking: Account number: 01-1839-0188939-00 or National Bank: Account number: 06-0869-0548507-00.
A flood of patients is expected to arrive at Christchurch Hospital with injuries from today's 6.3 magnitude aftershock.
More than 40 people had arrived at the hospital with quake injuries as at 2:15pm, with Civil Defence expecting that number to rise significantly.
Wellington Hospital is on stand-by to receive patients, a Civil Defence statement says.
Auckland District Health Board incident controller Margaret Dotchin says the region's hospitals are on a Code Red setting and ready to receive patients at short notice.
"We are in contact with agencies coordinating the earthquake response and have not had confirmation that there will be a need to transfer any patients to Auckland.
"However, we have set up an Incident Management Team for Auckland City Hospital and Starship," she says.
"We have 88 ward beds available and, if required, we have space available in our Intensive Care Unit.
TV3 reports water buckets are being taken from the Avon River to put out a fire at the CTV building on Madras Street.
Tourism Holdings Limited says it has closed its rentals branch but some crew will be on site during normal business hours.
"Those dropping off today are being contacted by phone and where possible being offered to retain the vehicle if no accommodation is available and the Airport remains closed."
Kiwi Experience inbound passengers to Christchurch over the next two days today are being accommodated outside of Christchurch.
Passengers due to start their journey tomorrow from Christchurch are being contacted to defer their start date.
Countdown says all of its staff in the Christchurch area have been accounted for and only a small number of minor injuries have been reported.
It says the majority of Countdown stores in the Christchurch area will remain closed overnight. Countdown Rangiora is currently open with skeleton staff.
Stores will not be re-opened until it is deemed safe to do so.
Federated has set up a 24-hour emergency phone line for members needing support or wanting to report damage after the Christchurch earthquake.
The number is: 0800 327 646
Alternatively, members can email email@example.com
Air New Zealand says services to and from Christchurch Airport remain cancelled up until 7pm this evening.
It will give another update after 7pm.
GNS Science reports that another aftershock struck at 5.19pm measuring 4.6. The 13th since the 6.3 earthquake at 12.51pm.
Labour leader Phil Goff who was at Christchurch Airport when the quake struck says it was immediately clear "it was a big one".
He says the city centre was "like a war zone" when he returned to it.
"There's damage to buildings that weren't damaged last time so our thoughts are with the people in Christchurch."
Mr Goff says he intends to stay in Christchurch and to go down to the command headquarters to see what reports he can get, "and what help we can give".
"This is a time for all of New Zealand to get behind Christchurch."
Millennium and Copthorne Hotels NZ says it believes all the guests and staff in its hotels have been evacuated.
It says it is too early to know the extent of the damage.
The New Zealand Blood Service says contrary to some media reports it does not need extra donations of blood following today's earthquake.
It says it has "sufficient stocks of blood at this time".
Telecom says its telephone boxes in Christchurch are going to have free calling enabled so people in the city can call for free.
BP Oil New Zealand says that all of its Christchurch service stations have been closed subject to inspection of ground based tanks and pipes after today's earthquakes.
They were shut as a precaution after either loss of power or damage to some forecourts.
BP NZ Managing Director Mike McGuinness says when the sites re-open, the available fuel will be quarantined for emergency services to ensure essential services can be provided to the city.
Westpac says all its Christchurch branches will be closed tomorrow.
Customers with queries should refer website or call 0800 400 600.
Australian Prime Minister Julia Gillard says Australia will provide any assistance requested by New Zealand, adding the search and rescue team is"literally on its way".
"There is likely to be a lot of searching to do under the rubble."
Australia's Attorney-General Robert McClelland says the search and rescue team from New South Wales is aboard a defence plane on its way to Christchurch.
If the city's airport remained shut the plane will land at the New Zealand air force base at Blenheim.
"The team will have search, rescue, medical, engineering and support capabilities," Mr McClelland says in a statement.
Lyttelton Port chief executive Peter Davie says the port has sustained "pretty major" damage in this afternoon's quake.
"[The damage] is bigger than last time, but what the recovery programme is we don't know yet," Mr Davie says.
He says none of the port's staff suffered any injuries in the quake, and it is unclear how long the facility would be closed for.
"At this stage we'll say 24 hours ... and we'll go from there."
Telecom's external communications manager Mark Watts says the fixed line network is "holding up pretty well", although in many instances only phones which do not require power are able to be used.
Emergency service lines are working but remained heavily congested.
The mobile network is also suffering from overloading and Mr Watts advised customers to only text and call if it was absolutely necessary.
He also said those affected by the quake should try to conserve their mobile batteries.
Civil Defence Minister John Carter says it is understood a number of significant hotels have been badly damaged and it is not known if they have been evacuated yet.
He says two companies of infantry are available to help police evacuate the central city.
"The most important point we want to address over the next 24 hours is the safety of the people."
Mr Carter says there is no detailed information about damage or casualties in Lyttelton, near the epicentre of the quake.
He says there are no specific details on damage to schools which are now closed. Teachers have been staying with pupils until they are collected by parents or guardians.
"Over time one of the things that might be useful is for them to think about whether they take a break from Christchurch."
Tower has set up an emergency response team to handle insurance claims following the latest earthquake.The number to call is 0800 808 808.
Civil Defence Minister John Carter says looting following the quake is a "a probability" but it is hoped it won't happen.
A second emergency Cabinet meeting will take place at 7pm and there will be an update after that.
Bill English says the Cabinet meeting will include an update on the situation and a focus on the welfare of people who can't get to their homes as well as maintaining search and rescue effort through the night.
The Auckland University Students' Association has launched an immediate street appeal to raise money for the people of Christchurch affected by today's massive aftershock.
Anyone wanting to make a donation should contact the association on (09) 309 0789, or make a donation in person around the Student Union Building on the University of Auckland campus.
The New Zealand Fire Service is mobilising its two North Island urban search and rescue taskforces to support the third taskforce based in Christchurch.
National Commander Mike Hall says the Canterbury earthquake is a national disaster and the Fire Service is responding with all its resources.
"Plans are under way to send fire appliances and personnel from other parts of the South Island to Christchurch to assist with the emergency response."
TV3 reports that 24 people are trapped on the 17th floor of the Forsyth Barr Building on Colombo Street after a stairwell collapsed. They are currently being rescued.
Geonet reports that another three aftershocks have occurred in the last 40 minutes. A magnitude 4.6 quake was measured 10km east of Lyttelton at 3.38pm. That was followed by another five minutes later, a 4.5 quake 10km south-west of Christchurch.
The third took place at 4.04pm and measured 4.6 on the Richter scale. It was centred within 5 km of Christchurch and took the total to 10 aftershocks since the 6.3 earthquake at 12.51pm.
Deputy Prime Minister Bill English international offers of help were offered almost immediately.
Civil Defence Minister John Carter says search and rescue teams from New Plymouth and Auckland should be on the ground within four or five hours.
He says rescue operations will continue through the night until all the buildings have been gone through and evacuated.
He says are no initial figures about casualties and "it wouldn't be prudent for us to speculate at this time".
Deputy Prime Minister Bill English says a security cordon will be established around central Christchurch.
He says two search and rescue teams are being flown into the city.
New Zealand has also taken up an Australian offer of search and rescue assistance.
Mr English says the Government is aware of the reports of fatalities but has not yet been able to confirm those.
Some of the injured have already been taken to hospitals outside Christchurch, he says.
Christchurch Cathedral Dean Peter Beck says while church staff had tried to get everybody out as the earthquake struck there are likely to be people still trapped.
He says he has no idea how many and the severe damage to the Canterbury icon including the collapsed steeple was nothing compared to the loss of life in other parts of the city.
"The people are the most important priority. I'll be encouraging the clergy to be out there reaching out to people."
Prime Minister John Key is set to land on an Air Force plane in Christchurch about 5pm, where he will address media.
Christchurch Mayor Bob Parker has declared a state of emergency and says Canterbury will need help from the rest of the country.
He says he holds grave concerns for the safety of people in Banks Peninsula area following today's massive 6.3 earthquake and aftershocks.
Christchurch is located immediately north of the peninsula.
"We still have yet to hear any reports in from Banks Peninsula and I'm very very concerned about that," he tells Radio New Zealand.
"The centre of the earthquake was in Lyttelton Harbour. There are hills covered in rocks, those rocks would have come down."
Mr Parker says the damage to the city centre is immense and people are trapped in buildings.
The New Zealand Transport Agency says the main roads out of Christchurch city are open following the quake but the Lyttelton Tunnel remains closed.
It says motorists should use extreme caution and should only drive if they have to.
The Ferrymead Bridge is reported to be impassable because of rising water.
Some suburbs in Christchurch appear to have escaped relatively unscathed from the earthquake, Herald reporter Jarrod Booker says.
Suburbs in the west of the city such as Hornby show no obvious signs of the damage to properties and roads which has been so severe in the central and southern parts of Christchurch.
Christchurch Police District Commander Superintendent Dave Cliff has returned to the city from Wellington to take personal command of the rescue effort. Commissioner Howard Broad is also on his way to Canterbury courtesy of an Air Force flight.
Police from other districts are likely be called to the city.
People having difficulty reaching emergency services through 111 are advised to be patient and if the first call does not go through, to hang up and call again, as there is network damage, congestion and overloaded lines.
A people finder page has been set up on Google.
KiwiRail has stopped all trains from Timaru to Picton, and on the West Coast because of the quake. There have been no injuries to staff or passengers.
A coal train derailed at Heathcote with seven wagons affected, but is still upright. There were no injuries, and the train driver reported cracks in the Martindale Bridge, so the police could stop traffic.
TranzAlpine and TranzCoastal services will not be running tomorrow.
Interislander services across Cook Strait are still operating as normal, although Civil Defence has asked people not to travel to Christchurch.
International media are reporting on the earthquake including BBC
CNN, the Sydney Morning Herald and Al Jazeera.
The managing director of Pyne Gould Corporation Jeff Greenslade said his company was trying to account for all of its staff after its building was damaged in the quake.
TV3 earlier reported that some 200 people were believed to be trapped in the Pyne Gould building.
"Obviously we're very much going through the process of accounting for staff. Finding out were all the people are."
TV3 reports that a body has been carried out of Christchurch's YHA hostel.
Civil Defence and Emergency Management has made contact with the Environment Canterbury Civil Defence, but has yet to make communication with Christchurch City Council Civil Defence.
Christchurch Hospital is now operational, with only one ward was damaged.
Christchurch Airport is still closed pending an inspection of the runway.
Since the 6.3 magnitude quake there have been at least six large aftershocks. Civil Defence says more are to be expected and each time one is felt people are advised to drop, cover, and hold on.
Civil Defence Minister John Carter said all the South Island hospitals apart from Invercargill had been emptied to make way for earthquake victims.
Mr Carter and preparations had been made for a state of emergency to be declared.
He said the number of fatalities and the extent of the damage was still unclear.
Jetstar announced that its domestic and transtasman international services to and from Christchurch were been suspended for the remainder of today until further notice.
Jetstar New Zealand services this afternoon to/from Auckland, Wellington and Queenstown were also affected and will not operate until further notice due to air traffic control.
Jetstar will soon issue a customer advisory offering flexible fare arrangements for travel.
A magnitude 5.5 aftershock has been recorded within five kilometres of Lyttelton - the town at the epicentre of a huge earthquake that hit Canterbury today.
The large aftershock was recorded at 2:50pm at a depth of 5km.
It was the sixth recorded by Geonet since a 6.3 magnitude quake caused widespread devastation and death at 12:51pm.
The largest, a 5.7 magnitude shock, was recorded at 1:04pm at a depth of 6km, 10km south of Christchurch.
Health Ministry communications manager Peter Abernethy said, at 1.20pm today, there had been reports of superficial damage at Christchurch
Hospital. Two wards had been evacuated because of loss of power.
He did not know where the patients were taken.
It was likely that other hospitals around the country would have to take patients from Christchurch. Plans for this were still uncertain and would depend in part on using Christchurch Airport, which was still closed. Moving patients out of the city by road would depend on roads and bridges being safe to use.
Nelson Hospital and Timaru Hospital were discharging patients who could be discharged, to free up beds for people from Christchurch. Other hospitals would probably begin doing the same.
Police have arrested a man who was "trying to be helpful" but getting in the way, reports TV3.
An Auckland International Airport spokesman said two flights - one a Pacific Blue, the other JetStar, had been diverted from Christchurch airport to Auckland.
Flights from Auckland airport itself were suspended after the Christchurch quake, while Airways, the state owned enterprise that looks after the nation's air traffic control system, checked out its Christchurch system.
Retailers across the country may be experiencing delays processing EFTPOS transactions in the wake of the earthquake, says Paymark. The delays are due to the huge pressure on Telecom's network, and will affect retailers using dial-up services.
The earthquake has not affected the Paymark network. Paymark asks that retailers remain patient and advise that services will return to normal once the volume of calls subsides.
The magnitude 6.3 earthquake in Christchurch today is still classed as an aftershock despite the scale of the damage.
"This earthquake struck much closer to the city so what we have seen today is a much closer and shallower shake. With many buildings weakened we are seeing much more damage," University of Canterbury Earth Sciences Professor John Townend told Radio New Zealand.
The quake today was definitely connected to the first magnitude 7.1 quake of September 4, he said.
"This is in one sense just one of those earthquakes following that but much larger than we have seen previously. At some point aftershock sequences do end. The rate does diminish but the magnitude doesn't. Any of them could be quite big."
The Provincial Chambers building is reported to have collapsed, with people trapped inside.
All Countdown supermarkets in the Christchurch area are closed.
Christchurch-based Herald reporter Jarrod Booker said the southern suburbs appeared to be particularly badly hit.
Liquefaction is forcing tarmac up in the middle of the road and water and sand are spewing out of chasms.
The third significant aftershock that hit Canterbury was at 2.39pm.
It was a magnitude 4 and centred at a depth of 8km, 10km north-east of Lyttelton.
A GNS Science spokesman said each aftershock increased the chances of buildings collapsing or being extensively damaged.
The 111 phone system in Southland is out of action following today's earthquake in Christchurch.
Anyone needing urgent assistance from the police must phone their local police station direct - this number is in the BLUE pages at the front of the Southland phone book.
Anyone needing an ambulance in Southland must phone 03 211 3044.
Anyone needing assistance from the Fire Service must phone the police, who may be able to redirect your call.
TV3 is reporting up to 200 people may be inside the Pyne Gould Guinness building on Cambridge Tce and screams can be heard from inside. A woman was rescued from the top of the building.
Civil Defence has alerted all Urban Search and Rescue teams in the city, and an Australian team is on call.
Temporary accommodation is being organised for those who have been displaced, with tents possibly to be erected in Hagley Park.
The hospital has been evacuated and several rest homes are also being considered for evacuation.
Flights in New Zealand are not taking off in the wake of today's 6.3 magnitude earthquake in Christchurch.
Auckland Airport spokesman Richard Llewellyn said the airways system around the country was closed shortly after the earthquake.
"For the moment planes are landing but no planes are departing,'' he told NZPA.
"The national air traffic control centre is in Christchurch, and they are checking to make sure it is all okay, and until then the airways system has been closed."
Air New Zealand says flights in and out of Christchurch have been cancelled until at least 7pm.
Another severe aftershock has hit Christchurch.
Herald reporter Jarrod Booker said queues of cars could be seen being shaken up and down as the aftershock hit.
He said cars were being rocked side to side while they were stuck in gridlock in the street and occupants could be heard screaming.
Speaking to media at the Beehive's National Crisis Centre, Director of Civil Defence John Hamilton said a response plan was now being put together using all available national resources.
"That includes extra fire people, extra police personnel, assets from the Defence Forces. International offers of assistance are coming through from Australia in particular."
Mr Hamilton said the earthquake was a level three crisis - the highest for a localised event.
Police say multiple fatalities have been reported at several locations in Christchurch CBD. They say two buses were crushed by falling buildings.
There are reports that there are no more ambulances available and police are evacuating injured people in their cars.
MFAT says people in Australia with fears for relatives can call: 1300 555 135.
Geonet reports a second magnitude 4.4 aftershock at 1.46pm, centred 10km east of Lyttelton at a depth of 5km.
A man says he and 19 other colleagues are trapped in Christchurch's Forsyth Barr building on Colombo Street.
Gary Moore told NZPA that workers were stuck on the 12th floor as the stairwell had collapsed. He was not sure if people were trapped on other floors.
People were in a state of shock but were not injured and he urged NZPA to let somebody know.
He described the first quake and the aftershocks as catastrophic.
"We watched the cathedral collapse out our window while we were holding onto the walls."
"Every aftershock sends us rushing under the desks. It's very unnerving but we can clearly see there are other priorities out the window. There has been a lot of damage and I guess people are attending to that before they come and get us," he said.
There are reports that all airspace in New Zealand has been closed following the earthquake.
Airways NZ, the national Air Traffic Control organisation, is based in Christchurch, and unconfirmed reports are coming in that it has been hit by the earthquake.
So far, four international flights have been diverted to Wellington Airport.
Herald reporter Jarrod Booker says there is still massive gridlock in the streets. Emergency services are struggling to get through the queues of traffic and are having to slowly manoeuvre their way through the traffic.
Some people are standing on the footpath just staring into space in shock.
"Multiple fatalities have been reported at several locations in the central city, including two buses crushed by falling buildings. A doctor and emergency services are attending," police said. There have been reports of fires in buildings and people trapped inside buildings.
One caller told Newstalk ZB: "It's taken me over an hour to get probably 1.5 - 2kms. We are trying to go around the city. I'm trying to get from one side of Christchurch to another."
A listener told Newstalk ZB that the Piko Wholefoods building on Kilmore Street near the city centre, which was hit in the September 4 earthquake, is now "practically non-existent".
Black Caps cricketer Scott Styris, in India for the World Cup, has tweeted: "Hope everyone in chch is ok. Some worried boys here in India. Be safe."
Roger Sutton, CEO of power company Orion New Zealand, estimates that electricity is down across 80 per cent of Christchurch, although there are pockets of Hornby and Riccarton that still have power.
"This is much, much more serious than last time," says Sutton, "We have some major power assets that have been damaged by this quake."
Sutton says Orion should have a better idea of when power can be restored by 5pm this afternoon.
Newstalk ZB AM frequencies are out and they are now broadcasting on 91FM, 97.7FM and 106.5FM in Christchurch.
Regarding reports of fatalities, Prime Minister John Key said "at this stage we can't comment. We simply don't know but we know there's been major buildings have collapsed. We have reports of people in the vicinity at the time."
Police have called in the Defence Force for assistance.
Police report Christchurch Hospital has not been evacuated and is in operation. Triage centres for the injured have been set up at Latimer Square (Central City) Spotlight Mall (Sydenham) and Sanitarium (Papanui).
Comment from 2Degrees:
"Our thoughts are with everyone in Christchurch right now. Our network remains operational for calls with the exception of three cell sites - all of our staff are ok. Some texts may be delayed, and please keep non-essential calls to the affected area to a minimum."
Geonet reports another earthquake of 4.5 struck at 1.21pm, 10km east of Diamond Harbour.
Prime Minister John Key:
"Obviously this earthquake has taken place at a time where people have been going about their daily business. We're doing everything we can to make sure that people are safe and are evacuating the central city.
"It's an extremely worrying situation for the people of Canterbury and will have significantly unnerved them and our sympathies and thoughts go to the people of Christchurch."
The police have confirmed multiple fatalities from today's quake.
Prime Minister John Key said the Beehive's Civil Defence bunker has been activated but there is still only in limited contact with Christchurch
"We cannot rule out loss of life. We're doing everything we can."
TVNZ reported that a body had been pulled from a car that had been hit by rubble.
Prime Minister John Key is currently making a statement in Parliament. An emergency cabinet meeting will be held at 3pm, after which he will fly to Christchurch.
The Fire Service has confirmed to Radio New Zealand there have been deaths.
Earthquake Recovery Minister Gerry Brownlee said he was in "deep shock" after receiving reports of today's quake.
He was "desperately" trying to get home from an overseas conference after receiving initial reports about extensive damage to Christchurch.
"My worry is for all the people that are affected. My thoughts are with my own family that are there."
Vodafone spokesperson Matt East said:
"We have a large number of sites down in the Canterbury region. There are about 43 sites running on battery back-up. Those sites will last, depending on the load on them, eight to 12 hours.
"We are asking people if they need to contact someone to please text them because it uses a lot less energy on the network and only call if you need to."
Civil Defence advice:
Check yourself first for injuries and get first aid if necessary before helping injured or trapped persons.
Assess your home or workplace for damage. If the building appears unsafe get everyone out. Use the stairs, not an elevator and when outside, watch out for fallen power lines or broken gas lines. Stay out of damaged areas.
Look for and extinguish small fires if it is safe to do so. Fire is a significant hazard following earthquakes.
Listen to the radio for updated emergency information and instructions.
Do not overload phone lines with non-emergency calls.
Help people who require special assistance - infants, elderly people, those without transportation, families who may need additional help, people with disabilities, and the people who care for them.
Detailed safety advice will come from local authorities and emergency services in the area. People should act on it promptly. MCDEM, local civil defence authorities and scientific advisers are closely monitoring the situation.
National Business Review reporter Chris Hutching told the NBR website: "The roads are running with water. It's like rivers everywhere. The shakes are happening every minute. There are constant aftershocks."
A "huge chunk" of the cathedral has reportedly collapsed and there are people trapped inside.
A TV3 reporter said the Pyne Gould building in Cambridge Tce had collapsed.
A transpower spokesman says there had been damage to the power grid, with power blackouts in the area. It was still too early to ascertain the extent of the damage.
The TVNZ building in Christchurch had collapsed, a source, who described the quake as "massive", told NZPA.
The Christchurch police central police station has been evacuated and there are reports of collapses of many buildings, including a church in the central city.
David Alexander told NZPA the quake had ruined his 1906 villa in Opawa, about 4km from the central city.
"It's done a lot of damage, it was really violent and quick. We've got glass everywhere. Our house has just been trashed."
His piano was tilted at a 45 degree angle, and had smashed a hole in a wall, the Christchurch photographer said.
The quake had been like thunder, with a big violent bang.
He was certain the three chimneys the house once had would have come down, had they not been removed after the September quake.
He could hear sirens in the streets as emergency services activated, while in his house wardrobes were over, cupboards open, and porcelain and smashed china was everywhere.
"That was frightening. We've got huge cracks in the roof we didn't have two weeks ago, when the inspectors came (to check damage cause by the September quake).
There are reports of people trapped in a building in Colombo St.
Media statement from Telecom: Telecom is working intensively to understand which services have been affected by today's earthquake and get these restored as soon as possible.
Our thoughts are with the people of Canterbury.
Christchurch International Airport says it is closed until further notice
Mayor Bob Parker described it as feeling like a brand new quake, saying he was "thrown quite a distance".
"That was, in the city central anyway, as violent as the one that happened on the 4th of September," he told Radio New Zealand.
Mr Parker said there were scenes of "great confusion" on the streets, and the roads were jammed as vehicles sought to get out of the central city.
"I know of injuries in my building and there are unconfirmed reports of serious injuries in the city."
Mr Parker did not know the extent of damage to the city's infrastructure, but advised people not to drink the water supply.
"We've been through this before this once, we now need to think we did at that time."
Christchurch resident Jane Smith who works in the central city told the Herald a work colleague had just returned from helping rescue efforts after a building facade had collapsed on a bus on Colombo St.
"There's people dead. He was pulling them out of a bus."
"Colombo St is completely munted."
"We can't move at the moment because the city's gridlocked."
The huge aftershock would have caused more shaking and more damage than the original 7.1 magnitude quake that hit Christchurch on September 3 last year, Geonet has confirmed.
Its data centre manager Kevin Fenaughty said residents said the quake's epicentre was located in the "worst possible location" for the city.
"It's a nightmare. A lot of people were just getting back on their feet after the original quake."
"We now need to think about all the things we learnt at that time (of the September 4 quake)," mayor Bob Parker said on Radio New Zealand.
"Emergency services now have the incredibly difficult task of navigating a city which is evacuating itself.
"We need to start the process of checking hundreds of people.
"I don't have an overview.
"That was as violent as the earthquake we had on the September 4th.
"We had a nasty shock again about 30 to 60 seconds later."
Christchurch major Bob Parker told Radio New Zealand that he's heard unconfirmed reports of some serious injuries.
Kodie Wixon - "Was out playing touch on hagley park, big rumble, ground was just shaking, it felt like i was drunk swaying around!"
The BusinessDesk news agency reported that the kiwi dollar dropped almost half a US cent from US76.32 cents immediately before the quake to US75.79 cents immediately afterwards.
Sky News reports that Christchurch Hospital has been evacuated.
Newstalk ZB reports people were running out of buildings and that liquefaction has been spotted on the eastern side of the city.
Several buildings that suffered damage from the September 4 earthquake have collapsed, according to reports.
Civil Defence spokesman Vince Cholewa said the National Crisis Centre has been triggered and was preparing what Government response there would be.
"The quake is significantly smaller than the previous Christchurch earthquake, however it was very shallow and might have been very close to the centre of the city," he said.
Mr Cholewa was not aware of any casualties or the extent of the damage.
"We are still getting a picture of what has happened and we are aware of the details."
Phone links have been cut to the city. Both Vodafone and Telecom said they were investigating. "We're checking the status of network in Christchurch and will update when we can," Vodafone said.
@edmuzik William rolleston has fallen backwards off his plinth, head fallen off
@edmuzik: Observatory in the arts centre has fallen down, may be builders in it
The quake was magnitude 6.3 at a depth of 5km, centred 10km southeast of Christchurch.
Tweet from Phil Goff in Christchurch:
Big #eqnz in Chch - glasses & plates smashing, we've just been evacuated from Chch airport.
Witness reports from Facebook:
"In Rangiora and it felt huge - hope Christchurch is OK"
"Felt it in dunedin"
"Felt it in queenstown!"
Witness reports from Facebook:
"bloody awful here nr Sheffield - house rolled up and down and shook violently for a good 10 secons or more - husband in town has no power - i am a shaking wrekc."
"Yes my house is a mess, feel bigger that the big one, way bigger"
"Felt huge. Everything smashed, furniture upturned. Very scary"
"Massive destruction I'm the inner city"
The earthquake was felt as far north as Wellington and as far south as Queenstown.
Phone lines are down so it's difficult to get information, but Herald reporter Jarrod Booker said in a brief phone call that they were experiencing a massive earthquake, "bigger than the original". He sounded very shaken.
View Christchurch earthquake: Map of the destruction in a larger map
- NZ HERALD STAFF, NZPA