The 8.9 magnitude quake struck Friday about 125 kilometers off Japan's coast, and prompted tsunami warnings across the Pacific — including areas as far away as South America and the entire U.S. West Coast.
A tsunami up to10 meters high inundated Japan's coastal areas. Television footage showed mud waves carrying vehicles, buildings and tons of debris over farmland in Sendai, the capital of Miyagi prefecture.
Japanese media say a ship carrying 100 people also was swept away in the massive wave.
The quake also was felt in Tokyo, where it shook buildings and caused several fires. All train and subway traffic in the city has been stopped. Several aftershocks have been reported there.
The U.N. nuclear agency says Japan has shut down the four nuclear power plants closest to the quake. Japanese authorities ordered about 2,000 people to evacuate the area around the Fukushima Daiichi nuclear plant north of Tokyo, but say no radiation leaks have been detected.
A fire was also reported earlier in the turbine building of the Onagawa nuclear plant in Miyagi.
Addressing the nation, Japanese Prime Minister Naoto Kan said the government would do everything it can to minimize the effects of the disaster. And in Washington, President Barack Obama said the United States is ready to help the people of Japan. The U.S. military in Japan has opened up the Yokota Air Base to some commercial flights diverted from Japanese airports.
The Hawaii-based Pacific Tsunami Warning Center said a tsunami warning was also in effect for Russia, the Philippines, Taiwan and Indonesia.
The International Federation of the Red Cross says it is monitoring the situation closely with the Japanese Red Cross and other local societies.