10.44pm Japanese Chief Cabinet Secretary Yukio Edano has confirmed the explosion at Fukushima-Daiichi to Reuters.
"We are looking into the cause and the situation and we'll make that public when we have further information," he said.
10.35pm Japan's Nuclear and Industrial Safety Agency is investigating the explosion at the Fukushima-Daiichi plant, according to the BBC.
Meanwhile, Chief Cabinet Secretary Yukio Edano says the government is collecting iodine, which can be used against radiation sickness.
10.30pm WeatherWatch.co.nz says winds are currently south-westerly - blowing any radioactive gas north east. This wind may affect populated places directly north of the power plant.
The forecast is for winds from the westerly quarter for the next several days - which would blow any toxic gas out to sea.
10.23pm Reuters reports that the UN's nuclear watchdog - the International Atomic Energy Agency - is urgently seeking information on the situation at the Fukushima plant.
10.20pm The government says the Tokyo Fire Department is sending a "hyper rescue team" to Fukushima.
10.11pm Japan's NHK TV says officials measured the level of radiation at the entrance of the Fukushima-Daiichi plant at about 3.30pm, and if people were exposed to that level for an hour they would receive the same amount of radiation they normally would in a year.
10.07pm The Kyodo News Agency says residents within 10km radius of Fukushima No. 2 plant are to be evacuated. All those within 10km of the No.1 plant were earlier evacuated.
9.57pm The Nuclear and Industrial Safety Agency has told NHK that two radioactive substances, cesium and radioactive iodine, have been detected near the plant's No.1 reactor.
This may indicate that some of the metal containers of uranium fuel may have started melting.
University of Tokyo Professor Naoto Sekimura said it was possible only a small part of the fuel may have melted and leaked outside.
9.17pm An explosion has been reported at a quake-hit Japanese nuclear plant.
AFP and Japan's NHK TV reported a blast at Fukushima No. 1 atomic plant, 250 kilometres northeast of Tokyo. The Tokyo Electric Power Company - which runs the plant - says four workers were injured.
Public broadcaster NHK showed delayed footage of smoke billowing from the site, also reporting that the reactor building had been destroyed.
8.22pm Nearly a quarter of a million people have returned to their homes in the Philippines after spending the night at temporary shelters inland.
The council said 224,243 people were moved off the coasts overnight, either on their own or using military trucks.
Small waves struck the country, but caused no damage or casualties.
8.15pm The Tokyo Electric Power Co. says there will be severe power outages over the weekend. Outages by rotation for at least a few weeks.
7.20pm Singapore has sent five search specialists and five search dogs to Japan.
The officers are from the Urban Search and Rescue (USAR) contingent, codenamed Operation Lionheart.
Four of them returned from Christchurch on March 6 after participating in search and rescue efforts here.
7.05pm Japanese Prime Minister Naoto Kan is sending 50,000 troops for the rescue and recovery efforts following yesterday's earthquake.
The official death toll stands at 413, while police said between 200 and 300 more bodies were found along the coast in Sendai, the biggest city in the area near the quake's epicentre.
There are 784 people missing and 1,128 injured.
More than 215,000 people are living in 1,350 temporary shelters in five prefectures, or states, according to national police.
6.40pm An official with Japan's nuclear safety commission says that a meltdown at a nuclear power plant affected by the country's massive earthquake is possible.
Ryohei Shiomi said officials were checking whether a meltdown had taken place at the Fukushima Dai-ichi power plant, which had lost cooling ability.
Shiomi said that even if there was a meltdown, it wouldn't affect humans within a 10km radius.
6.27pm The Tokyo Electric Power Co. has warned of blackouts in a wide area of Japan, not just in quake-hit areas, says the Kyodo News Agency.
Electricity is in short supply after its power facilities were damaged by the earthquake.
TEPCO is asking people to conserve electricity.
Civil Defence says no further tsunami threat exists for New Zealand. Minor fluctuations in sea level may continue for up to 48 hours and caution is required on beaches and in marine environments.
5.42pm More than 45 countries have offered to help Japan, according to the United Nations.
5.35pm Thousands of people remain trapped in buildings surrounded by swirling floodwaters in Miyagi prefecture, authorities have told AFP.
5.05pm Japanese police say the combined number of people who died or are unaccounted is more than 1,200.
The death toll has reached 398, with the number likely to rise to well over 1,000.
Meanwhile, 805 people remain missing.
4.58pm New South Wales will send a 76-person specialist urban search and rescue team to Japan following the country's devastating earthquake.
The team will be made up of firefighter rescue specialists, supported by two structural engineers, eight paramedics, two doctors, and a police specialist.
Japan's Prime Minister Naoto Kan has inspected a quake-hit nuclear power plant in Fukushima.
"I realised the huge extent of the tsunami damage," Kan told the Kyodo News agency.
He said there were munute amounts of radiation being released from the plant.
The Tokyo Electric Power Co. has warned of power shortages and an "extremely challenging situation in power supply for a while", as several of its nuclear power plants just north of the city remain under close scrutiny.
The Japan tsunami disaster marks a rather macabre milestone in such global events - it's the first one where the world has watched as the disaster unfolds on their TV screens, live. Cameras showed the brown mass of water and debris inundating the town of Sendai and surrounding fields last night, as the event happened.
A strong 6.8-magnitude aftershock has struck off the east coast of Japan, US seismologists said, less than 24 hours after a massive earthquake created a powerful and destructive tsunami.
The aftershock, which the US Geological Survey said hit at a depth of just 24 kilometres, was centred 174km east-southeast of the city of Sendai, the scene of huge devastation when a 10-metre tsunami struck yesterday.
Officials monitoring tidal levels on the coast of Latin America and South America report only small waves coming ashore, following the tsunami near Japan.
The official death toll from Japan's earthquake/tsunami disaster now stands at 402 - but the Kyodo News agency says it estimates that more than 1000 people died.
A number of US Pacific Fleet ships in the Western Pacific, including an aircraft carrier, are converging on Japan to be in the best position to help those in areas damaged by the massive earthquake and subsequent tsunami.
A gallery of dramatic Reuters photos out of Japan here on The Atlantic website.
3.07pm: Good news - Japanese naval and coastguard helicopters have found a ship that was swept out to sea by the tsunami and have airlifted all 81 people aboard to safety, the Jiji Press reports.
The ship was owned by a shipbuilder in Ishinomaki, Miyagi prefecture.
2.12pm: The Pacific Tsunami Warning Centre has reduced the number of places in its tsunami warning list.
Warnings still apply for Japan, Russia, Mexico, French Polynesia, Pitcairn Island, Guatemala, El Salvador, Nicaragua, Antarctica, Panama, Honduras, Chile, Ecuador, Colombia, and Peru.
People should still follow any advisories/warnings from their local authorities.
The New Zealand Tsunami Expert Panel assessment is that there is still a marine and minor land threat only for parts of the upper North Island coasts of New Zealand.
A minor land threat still exists for Northland between Ahipara and the Karikari Peninsula as well as in the Bay of Islands and the Chatham Islands, while a marine threat remains for the northern North Island from Kaipara to Ahipara and south of the Karikari Peninsula, around the Coromandel Peninsula and Bay of Plenty to Gisborne.
2.01pm: Major tsunami warnings remain in place for the majority of the east coast of Japan, while tsunami warnings and advisories are in place for the remainder of the country's coastline.
1.57pm: The US Agency for International Development is dispatching a Disaster Assistance Response Team to Japan and has mobilised its partners, the Fairfax County Urban Search and Rescue Team and the Los Angeles County Search and Rescue Team. Each USAR team consists of around 72 personnel, search and rescue canines and around 75 tonnes of rescue equipment.
Meanwhile, search and rescue teams from the UK - the International Rescue Corps and Rapid UK - say they are on standby having both formally offered their services, the BBC reports.
1.45pm: Japan has declared a state of emergency at another nuclear power plant after a cooling system at its three reactor units failed following a massive earthquake. There has been no radiation leak.
Japan's nuclear safety agency is also set to order a plant operator of another plant to release slightly radioactive vapor to protect the reactor from damage.
Altogether, five reactor units - two at the Fukushima No. 1 plant and three at nearby Fukushima No. 2 plant - are in a state of emergency. All five plants have shut down.
Officials said earlier that only one of the two Fukushima No. 1 plant's units had cooling problems resulting from power outages. They now say both units are troubled.
1.38pm: Members of the local Japanese community are monitoring events closely.
Auckland Japanese Society chairman Masa Sekikawa says many have been glued to their TVs since the quake struck.
Tomorrow's planned Japanese Festival in Auckland looks set to be a day of mourning, he said.
1.15pm: Professor Polat Gülkan, President of the International Association for Earthquake Engineering has told the Science Media Centre there is no causality link between yesterday's quake off Japan and the February 22 quake in Christchurch.
"They are both on the same so called Pacific Ring of Fire belt but are so far from one another that it's a very remote possibility that one triggered the other. The Christchurch event was magnitude 6.3, so this magnitude 8.9 one packed about 8,000 times more energy but was much further removed from any urban area, so its effects in terms of ground shaking were milder. The tsunami waves are really one way of transporting the energy released by the earthquake to points farther."
12.58pm: Prime Minister John Key says New Zealand will send six Urban Search and Rescue staff to Japan immediately to help with earthquake efforts.
The six will travel to Japan tonight and the balance of a team of 48 would probably leave tomorrow, following a request from Japan, he said this afternoon.
12.39pm: Australian Foreign Minister Kevin Rudd says Japan will receive "the same" amount of assistance New Zealand received following the February 22 Christchurch earthquake. He says a sniffer dog team will be sent to Japan this evening and pledged any other assistance requested will be provided. Mr Rudd said the images broadcast from the devastated region are "stomach turning".
He said 11,000 Australians are understood to be resident in Japan, with "hundreds" estimated by the embassy to be in the affected area, including a large number of language teachers.
Australians looking for information on missing loved ones and Australians in Japan registering with the Australian Government that they are ok, should call the Department of Foreign Affairs and Trade on 1300 555 135.
12.11pm: Japan's nuclear plant operator, Tokyo Electric Power, said that a second of its atomic plants in an earthquake-hit area was experiencing reactor cooling problems, the Kyodo News agency is reporting.
12.01pm: The earthquake that hit Japan was the strongest in the area for nearly 1200 years, says a senior science advisor for the US Geological Survey.
David Applegate said the quake likely caused "tens of millions of dollars" in structural damage in Japan.
11.44am: The Japanese Urban Search and Rescue team have left Christchurch this morning to return to Japan in the wake of last night's earthquake and tsunami.
The team, who have been assisting with rescue and recovery operations in Christchurch following the February 22 quake, was planning to leave the city this weekend but brought forward their departure to help with rescue efforts in Japan.
Civil Defence National Controller Steve Brazier thanked the team members for their efforts in assisting with the Christchurch rescue efforts and has sent his condolences to the people of Japan.
Search and Rescue teams from New Zealand have also been requested by Japan, the United Nations says.
At least four teams have been requested by Japan, Elisabeth Byrs, spokeswoman of the UN Office for the Coordination of Humanitarian Affairs; New Zealand, Australia, South Korea and the United States, said.
UN Secretary-General Ban Ki-moon said the UN would do all it could to mobilise humanitarian assistance and disaster risk reduction teams as soon as possible to the earthquake- and tsunami-ravaged areas.
11.18am: Chile has ordered an evacuation of coastal zones at risk from the massive tsunami sweeping across the Pacific, Interior Minister Rodrigo Hinzpeter said.
The evacuation order was for "all people living in defined flood zones." He described it as a "preventative" move.
Many of the 524 killed in last year's Chilean earthquake died as a result of a tsunami triggered by the quake.
11.11am: Google has launched a people finder - similar to the one created following last month's 6.3 magnitude quake in Christchurch - to help people get in contact with missing friends and family in Japan.
10.51am: Prime Minister Naoto Kan has ordered the evacuation of all residents within 10km of the Fukushima No. 1 nuclear power plant, the Kyodo News agency is reporting. Mr Kan is currently making his way to the affected areas in the country's northeast by helicopter.
The amount of radiation has reached around 1000 times the normal level in the control room of the No. 1 reactor of the Fukushima No. 1 nuclear power plant, the Nuclear and Industrial Safety Agency told Kyodo News.
10.35am: Radio New Zealand is reporting that waves reached 30 metres inland on the island of Ua Pou in the Marquesas Islands, but caused no serious damage. An official told local radio the wave measured about 50cm.
10.03am: The tsunami has destroyed much of Crescent City harbour in California, near the Oregon border, the Los Angeles Times reports.
Several people are believed to have been washed out to sea, including one man who was taking photos of the tsunami.
Residents say around 30 boats were crushed in the harbour, with water destroying most of the docks.
Crescent City was hit by a tsunami in 1964 which killed 11 people and destroyed nearly 300 homes and businesses.
The harbour was also hit badly by tsunami-driven currents in 2006, doing US$10m worth of damage.
9.46am: Japan Today is reporting that four trains are unaccounted for in the Miyagia and Iwate prefectures.
9.15am: The tsunami surge has now been registered in Gisborne and Tauranga, according to the Tsunami Gauge Network.
9.03am: The Tokyo Electric Power Company has decided to release air that may contain radioactive materials from containment vessels at Fukushima Number One Plant to avoid their breakdown, the Japanese broadcasting corporation NHK is reporting.
Tokyo Electric says the amount of air to be released will be small and that it will notify residents near the plant before it starts releasing the air.
8.49am: Water rushed onto roads and into hotel lobbies on Hawaii's Big Island and low-lying areas in Maui were flooded as two-metre waves crashed ashore.
The tsunami warning has been downgraded to an advisory in Hawaii, but officials said people should still stay away from beaches.
8.24am: Mexican President Felipe Calderon has tweeted that the tsunami has reached Ensenada but has not exceeded the high tide mark.
"First and second wave in [Baya California] were 70 cm. Some experts say that the third wave may be strong and dangerous," he wrote.
Mexico's tsunami alert remains in place.
8.03am: The tsunami has reached North Cape, Raoul Island, Great Barrier Island and East Cape, according to GNS Science's Tsunami Gauge Network.
Far North Civil Defence controller Alastair Wells told Radio New Zealand a surge of around 20cm is expected initially, but this is forecast to build up to 1m within the next three hours.
The tsunami marine warning will remain in place until an all clear is pronounced, Mr Wells said.
7.50am: The tsunami has damaged boats in the San Francisco Bay Area, the ABC has reported.
The water reportedly dropped by about 9 feet (2.7m) at Santa Cruz's harbour as water was sucked out to sea around 8.10am Pacific Standard Time (5.10am NZST).
Several boats broke loose and part of a dock was also pulled away during one of several surges, each of which took about 10 minutes.
Harbour officials have advised the public to evacuate the area and shelters have been set up along the west coast of the US for residents in the impacted area.
7.34am: There have been at least 95 aftershocks off the coast of Honshu, Japan, since the 8.9 magnitude quake, 16 of which were greater than magnitude 6. The 8.9 earthquake is the largest to ever hit Japan and the sixth-largest in the world since records began.
View Magnitude 8.9 earthquake triggers huge tsunami in a larger map
7.28am: The Pacific Tsunami Warning Centre has issued a tsunami warning for New Zealand in response to the earthquake. Wave heights of up to four metres have been measured in coastal Japan.
Wave heights of 0.2m have been observed in Nauru and in the Solomon Islands capital of Honiara.
Civil Defence says there is a minor land threat only for parts of the upper North Island coasts of New Zealand.
Based on real-time tsunami modelling and comparison with historical events, the interpretation is that a minor land threat - wave heights of just over 1m - now exists in Northland between Ahipara and the Karikari Peninsula as well as in the Bay of Islands and the Chatham Islands.
Passage of the wave through the South Pacific has been observed, however there is no indication of wave arrival in the Kermadec islands.
It was expected the first wave to arrive at New Zealand would reach North Cape at approximately 6.23am, however monitoring of the propagation of the tsunami across the Pacific indicates that actual arrival times may be approximately an hour later than first indicated.
7.16am: New Zealand Ambassador to Japan, Ian Kennedy, told Radio New Zealand 3500 Kiwis are known to be in Japan for more than three-month stays, but over 30,000 New Zealanders visit Japan each year.
"I guess you can add about 3000 to the 3500 and that would be about it. But that's just a guess," he said.
Mr Kennedy said with telephones down, authorities are using Skype and Facebook to reach New Zealanders in Japan.
People concerned about friends and family in Japan should contact the Ministry of Foreign Affairs and Trade on 0800 432 111.
6.56am: US President Barack Obama said the earthquake and tsunami was a "potentially catastrophic disaster".
"Today's event shows us how fragile life can be," he said.
Mr Obama said one US aircraft carrier was in Japan and another was on the way. He said the US would assist as required by Japan.
The tsunami has hit the US territory of Guam and the state of Hawaii, but Mr Obama said there had been no reported damage in the United States.
6.40am: Police in Japan say between 200 and 300 bodies have been found in the northeastern coastal city of Sendai, the city in Miyagi prefecture closest to the epicentre of yesterday's earthquake.
Another 137 have been confirmed killed and 531 are missing. Police also said 627 people had been injured.