A devastating tsunami triggered by the biggest earthquake on record in Japan was expected to have claimed more than 1,000 lives along the northeastern coast on Friday, after a wall of water swept away everything in its path.
Thousands of residents were evacuated from an area around a nuclear plant after radiation levels rose in the reactor, but there was no word on whether there had actually been a leak.
Underscoring grave concerns about the Fukushima plant some 240 km (150 miles) north of Tokyo, U.S. Secretary of State Hillary Clinton said the U.S. air force had delivered coolant to avert a rise in the temperature of the facility's nuclear rods.
The unfolding disaster in the wake of the 8.9 magnitude earthquake and 10-metre (33-feet) high tsunami prompted offers of help from dozens of countries.
China said rescuers were ready to help with quake relief while President Barack Obama told Japanese Prime Minister Naoto Kan the United State would assist in any way.
The United Nations said on Friday that "Japan has requested international search and rescue teams, but only a handful."
Earlier, the world body said that some 68 search and rescue teams from 45 countries were on standby, awaiting a request from Tokyo.
Stunning TV footage showed a muddy torrent of water carrying cars and wrecked homes at high speed across farmland near the coastal city of Sendai, home to one million people and which lies 300 km (180 miles) northeast of Tokyo. Ships had been flung onto a harbor wharf, where they lay helplessly on their side.
Boats, cars and trucks were tossed around like toys in the water after a small tsunami hit the town of Kamaichi in northern Japan. An overpass, location unknown, appeared to have collapsed and cars were turning around and speeding away.
Japanese politicians pushed for an emergency budget to fund relief efforts after Kan asked them to "save the country," Kyodo news agency reported. Japan is already the most heavily indebted major economy in the world, meaning any funding efforts would be closely scrutinized by financial markets.