SKY NEWS VIDEO A 33ft tsunami has killed at least eight people as it swept over Japan's northeastern coast after a 8.9 magnitude megaquake near the capital Tokyo.
The huge wave hit the port in the country's Sendai city, sending ships crashing into the shore and carrying cars and buildings through the streets of towns.
Mass evacuations are taking place after Tsunami warnings were issued for the entire Pacific coast.
The earthquake has obliterated Tokyo's Disneyland car park and caused large fires at sites including an oil refinery in nearby Iichihara.
Large aftershocks continue to hit the capital, following an initial tremor so strong it was felt 1,500 miles away in the Chinese capital Beijing.
Japanese prime minister Naoto Kan said there had been no nuclear plant radiation leak caused by the disaster.
But airports and portshave been closed and the Shinkansen 'bullet' train stopped.
Millions of homes are without power and Tokyo's fire department reported several people were injured when a roof caved in at a graduation ceremony in the city.
Among the countries issued with alerts from the Pacific Tsunami Warning Center in Hawaii are Guam, Taiwan, the Philippines, Indonesia, Hawaii and Australia.
Russia, South America, Marcus Island and the Northern Marianas have also been put on alert.
Russian authorities on the fareastern Sakhalin Island and nearby territories have evacuated some 11,0000 residents from coastal areas in anticipation of tsunami waves.
In downtown Tokyo, large buildings shook violently and workers poured into the street for safety after the tremor struck.
Experts say the earthquake is the world's fifth strongest since 1900.
The Japanese government's top spokesman, Yukio Edano, said the country was sending troops to the quake-hit area to join relief efforts.
TV footage showed a large building on fire and bellowing smoke in the Odaiba district of the city.
Police and coast guard officials said they were assessing possible damage from the quake
Several quakes had hit the same region in recent days, including a 7.3 magnitude one on Wednesday.
A megaquake is defined as one exceeding seven on the Richter scale.
