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. Whole villages have been washed away and at least one town has been largely destroyed.
The disaster was triggered by an 8.9-magnitude earthquake, the country most powerful since records began. Japan's military has mobilised thousands of troops, hundreds of planes and dozens of ships.
The tremor struck in the afternoon local time on Friday at a depth of about 24km, 400km north-east of Tokyo. It was nearly 8,000 times stronger than the one which devastated Christchurch, New Zealand, last month, scientists said.
About 300 people are known to have died and more than 700 are missing. Japanese media says the death toll will exceed 1,300.
Prime Minister Naoto Kan was to hold an emergency cabinet meeting early on Saturday, before visiting the disaster zone by helicopter.
The country's military has mobilised thousands of troops, 300 planes and 40 ships for the relief effort.
US President Barack Obama said a US aircraft carrier was already in Japan, and another was on the way.
The quake triggered a tsunami up to 10m, with waves of 7m battering the Japanese coast. A muddy torrent of water swept cars and homes far inland, turning residential areas and paddy fields into a lagoon of debris-filled sea water.
One of the worst-hit areas was the port city of Sendai, in Miyagi prefecture, where up to 300 bodies have been found in one ward alone. The town of Rikuzentakada, in Iwate prefecture, seemed mostly under water, with barely a trace of any buildings.
Japan Railways said it could not trace four trains along the north-eastern coast. A ship carrying 100 people was also reported missing.
Swathes of Kesennuma, in Miyagi prefecture, have burned into the night, while one-third of the city was said to be under water. Some 1,800 homes were reported to have been destroyed in the city of Minamisoma, Fukushima prefecture.
And a dam burst in north-eastern Fukushima prefecture, sweeping away homes, Kyodo news agency reported.
Meanwhile, Japanese authorities declared a state of emergency at five reactors at the Fukushima 1 and 2 plants, as cooling systems failed because of the earthquake.
They also warned there could be small radiation leaks as steam was released from the reactors, where pressure was reported to be considerably higher than normal.
More than 50 aftershocks - many of them more than magnitude 6.0 - have rattled the country.
In central Tokyo, a number of office workers have spent the night in their offices because the lifts stopped working. Millions of commuters were stranded overnight, while others walked home, after train services were suspended.
The tsunami rolled across the Pacific at the speed of a jetliner but had weakened before it hit Hawaii and the US West Coast. In the immediate aftermath of the quake, a tsunami warning extended across the Pacific to North and South America, where many other coastal regions were evacuated. (BBC).