The 8.9-magnitude tremor, which was centered near the northeast coast of Japan, killed hundreds of people and created 30-foot walls of water that swept across rice fields, engulfed entire towns, dragged houses onto highways, and tossed cars and boats around like toys. Some waves reached six miles (10km) inland in Miyagi Prefecture on Japan's east coast.

Buildings collapsed by the score, and numerous fires were ignited. Hundreds more people are missing, Japanese media reported, citing local and national police. Tens of thousands of people were displaced, according to Japan's Kyodo News Agency.

Kyodo predicted the death toll would surpass 1,000. The news agency, citing Japan's defense forces, also said 60,000 to 70,000 people were being evacuated to shelters in the Sendai area of Miyagi Prefecture.

Japanese Prime Minister Naoto Kan said the "enormously powerful" earthquake had caused "tremendous damage over a wide area."

The quake, which struck at 2:46 p.m. on March 10, prompted the US National Weather Service to issue tsunami warnings for at least 50 countries and territories.

The epicenter of Friday's main quake was located off Miyagi Prefecture, about 230 miles (370km) northeast of Tokyo, the US Geological Survey said.

Humanitarian agencies were working with rescue crews to reach people affected by the earthquake and tsunami.

Video aired by Japanese broadcaster NHK showed extensive fires in Miyagi and in the port city of Hakodate, in the southern part of Hokkaido island in northern Japan. An oil refinery was burning in Chiba Prefecture near Tokyo, according to NHK. And Kyodo News said fires could be seen in extensive areas of Kesennuma in Miyagi.

Aerial views of Kesennuma showed plumes of white smoke emanating from the center of the city and large, black areas the flames had already traversed.

A leak occurred in an atomic power plant in northeast Japan, a spokesman for Japan's nuclear agency said Saturday. Cooling equipment stopped working when generators failed in the quake, and the temperature inside the plant in the Fukushima prefecture had risen; officials lowered the pressure inside the plant hangar by venting it.

But high levels of radiation led officials to suspend the release, NHK said. Alternative plans were being evaluated, the broadcaster said.

Citing Japan's nuclear safety agency, Kyodo said radiation levels were 1,000 times above normal in the the control room of the facility's reactor.