BBC News with Iain Purdon

Japan has asked for international help as it battles to cool nuclear reactors at a power station damaged in Friday's earthquake and tsunami. Nuclear regulators in the United States say they've been asked to provide water and other resources to the Fukushima plant. The head of the United Nations nuclear agency, Yukiya Amano, said the IAEA has also been asked for help. Kerry Skyring reports from Vienna.

Yukiya Amano gives a

reassuring

assessment of Japan's handling of its nuclear crisis. The plants have been shaken, flooded and cut off from electricity, he says, and their workers have suffered personal tragedies. But despite all that, the reactor vessels have held, and radioactive release is limited. He does not believe that will

resemble

the disaster at Chernobyl 25 years ago. Responding to criticism that his agency was slow to provide information to the public, he said he will not try to second-guess the people on the ground. He described the events of the last few days as "truly unprecedented".

Millions of people in the affected areas of Japan's northeast are spending a fourth night without water, food, electricity or gas.

The Kyoto news agency says more than 500,000 people have been left homeless by the earthquake andtsunami. Communications networks are still down in many areas.

About 2,000 bodies were found washed ashore along the coastline on Monday, and aftershocks continue to be felt