A mammoth relief mission is swinging into action in north-east Japan, a day after it was struck by a devastating tsunami, claiming hundreds of lives.
The disaster was triggered by an 8.9-magnitude earthquake which struck at 2.46pm local time on Friday, at a depth of 24 km. It was centred 130 km east of Sendai, a port city on the northeastern coast.
Tsunami waves up to 10 metres high swept away homes and other buildings, vehicles, and overturned ships.
Whole villages have been washed away and at least one town with more than 20,000 inhabitants has been largely destroyed.
A huge relief operation is under way after the quake which killed more than 600 people, with hundreds more missing and it's feared 1,300 may have died.
Japan's military is sending 8000 troops, 300 planes and 40 ships for the relief effort.
A massive explosion struck a quake damaged nuclear power plant with Japanese officials fearing a meltdown at one of the plant's reactors after radioactive material was detected outside it.
US President Barack Obama said a US aircraft carrier was already in Japan, and another was on the way.
Television footage showed a huge wave of mud, water, a ship and building wreckage rolling across fields and buildings near the port city of Sendai, home to about 1 million people.
It showed cars and trucks being swept off a damaged bridge into water, boats being swept away - some overturned - and water rising around buildings. Sendai airport was flooded.
Police on Saturday said 200 to 300 unidentified bodies were found in Sendai reports Japan's public broadcaster NHK.
The northeastern city of Kesennuma, with a population of 74,000, has been hit by widespread fires and one-third of the city is submerged, the Jiji news agency reported.
Four trains are missing along the coast, the BBC reports.
However a ship with 81 people on board swept away by the tsunami was found and all on board airlifted to safety, the ABC reported.
The Fire and Disaster Management Agency says almost the whole city of Rikuzentakata, which has a population of 23,000 and is in Iwate prefecture, has been flattened by the tsunami, NHK reported.
The Kyodo news agency says 1800 houses have been destroyed in Fukushima prefecture.
There are reports an irrigation dam broke and swept away houses in the district.
Elsewhere in Japan several people are known to be buried in a landslide.
Kyodo news agency reported that in one of the worst-hit residential areas, people buried under rubble could be heard calling for help.
Oil refineries shut
Japanese prime minister Naoto Kan says there is major damage across a large area.
Car plants, electronics factories and oil refineries have shut across large parts of Japan and many sections of expressways have been damaged.
A fire is burning out of control at an oil refinery at Ichihara, near Tokyo, and the bullet trains in the north of the country have been stopped.
Several airports, including Tokyo's Narita, have been closed and all of the country's ports are closed.
Power is said to have been cut to millions of homes.
Strong quakes were also hitting northwestern Japan after the massive quake struck northeastern Japan, NHK public broadcaster reports.
Largest quake to hit Japan
The United States Geological Survey says the earthquake was centred near the east coast of the island of Honshu, 373 km from Tokyo.
At magnitude 8.9 it is in the top classification, a powerful earthquake.
It is the biggest quake ever to hit Japan and followed two major quakes earlier in the area.
More than 50 aftershocks, many of them more than magnitude-6.0, have rattled the country.
Two strong earthquakes, one measuring 6.7, also struck the mountainous Niigata district northwest of Tokyo, causing landslides and avalanches.
In central Tokyo, a number of office workers spent the night in their offices because the lifts stopped working, the BBC said.
Millions of commuters were stranded overnight, while others walked home, after train services were suspended.
At least 20 people were injured in Tokyo when the roof of a hall collapsed on to a graduation ceremony.