UPDATE: Police say there are reports of multiple fatalities at several locations in central Christchurch, following this afternoon's 6.3 magnitude earthquake.
The central city is being evacuated as police receive reports of widespread damage to buildings and infrastructure.
"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 persons trapped inside buildings.
Christchurch Hospital is not evacuated and is in operation, but the airport is closed and other airports have been affected.
Triage centres have been established for people with injuries at Latimer Square in Central City, Spotlight Mall in Sydenham and Sanitarium in Papanui
GNS Science said the 6.3 magnitude quake struck at 12.51pm, 20km southeast of Christchurch, at a depth of 5km.
Prime Minister John Key is holding an emergency Cabinet meeting and will fly to Christchurch after that.
Civil Defence Minister John Carter said cellphone and landlines were down and Civil Defence was using HP and satellite phones to try to communicate.
"We understand it is a lot shallower than the last one, it's closer than the last one and the effects may be worse."
The spire on the Christ Church Cathedral has tumbled in the quake.
Christchurch Mayor Bob Parker said an emergency operation was being set up. In the central city the earthquake felt as violent as the 7.1 earthquake on September 4.
"This is obviously a dreadful, dreadful aftershock, it felt more like a new quake to me," he told Radio NZ.
"What I can see from where I'm from..there's a significant amount of additional damage."
He said pipes were burst on the street.
"The waste water pipe has broken."
There were unconfirmed reports of serious injuries, he said.
"Emergency services now have the incredibly difficult task of moving through a city which is evacuating itself from the central city area."
He warned people not to block the streets.
"Our roads are now our lifeline, we need to get people out of the city."
"[We] need to make sure our people are as safe as possible."
Labour leader Phil Goff was among those evacuated from Christchurch Airport. He said he was surrounded by scared and upset people. He has now gone to Mr Parker's office 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.
The Christchurch Police Station was initially evacuated but is operational again.
Lincoln University lecturer Farhad Dastgheib was in a seminar with about 40 people when the quake hit.
"It went for about 30 seconds and people were very scared. We had two big ones and everyone was shocked and jumping under the tables but we were in a seven storey building so I don't know if that would have helped."
"This was during the day time and so we were there from the beginning. It felt like giant waves."
Mr Dastgheib's 19-year-old daughter Negin was at university when it happened. She said she completely lost her balance and saw a five-storey building swaying in front of her.
"We were all running around, some people were crying and some laughing hysterically. We are staying outside even though it's raining, we are too scared to go inside."
Radio New Zealand reported the town centre was packed with people, hugging and crying, while the concrete had lifted in places with trees uprooted and the Avon River has turned brown to liquefaction.
The quake was felt from Kapiti Island in the North Island to Gore in the South Island.
The Ministry of Civil Defence and Emergency Management said the national crisis management centre had been activated.
The quake was very shallow and information was still being gathered, a spokesman said.
Telecom said it was investigating reports all Christchurch phone lines were down.
The kiwi dollar fell 0.5c on the news of the earthquake.
A massive 7.1 tremor hit Canterbury on September 4 last year, causing extensive damage and a handful of injuries, but no deaths.
Thousands of aftershocks have since rattled the region.
The September quake caused billions of dollars of damage, with more than 168,000 claims to the Earthquake Commission.
Twitter users have reported feeling the quake in Wellington and Dunedin.
Herald reporter Jarrod Booker said people had left buildings and were out on the street.
He said the shake lasted approximately a minute and was extremely violent - rocking buildings back and forth.
Tarmac on the roads have cracked and water mains have burst, flooding the streets, he said.
He said the carpark at the Christchurch Star newspaper offices had turned into a river with huge cracks and the roads had risen in areas.
People were comforting people outside amid a general state of shock as people tried to absorb what had happened, he said.
Do you know anyone from or formerly of Rotorua affected by today's quake? Email news@dailypost.co.nz or phone 07 348 6199 ext: 57059.
Deaths in Christchurch quake
NZPA and staff
Rotorua Daily Post·
5 mins to read
UPDATE: Police say there are reports of multiple fatalities at several locations in central Christchurch, following this afternoon's 6.3 magnitude earthquake.
The central city is being evacuated as police receive reports of widespread damage to buildings and infrastructure.
"Multiple fatalities have been reported at several locations in the central city, including two
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