Rescue workers from more than a dozen countries searched ravaged northeastern coastal cities on Monday for survivors of a massive earthquake and tsunami, as an international effort to help Japan cope with its multiple disasters gathered pace. 

Some 70 countries have offered assistance in an outpouring of solidarity with Japan, with help coming not only from allies like the US but also countries with more strained relations like China, and even from the Afghan city of Kandahar.

"We have offered our Japanese friends whatever assistance is needed, as America will stand with Japan as they recover and rebuild," said White House spokesman Jay Carney.

He said two US urban search and rescue teams, with 144 staff and 12 dogs, had begun work at first light on Monday looking for people trapped in the rubble in buildings flattened by the tsunami that followed Friday's 8.9-magnitude quake.

A 15-member Chinese rescue team was also at work in the main quake zone after landing in Tokyo on a special chartered flight on Sunday, Chinese state news agency Xinhua said.

Setting aside the acrimony over Japan's wartime atrocities that underpins widespread Chinese public distrust of Japan more than six decades after the end of World War Two, Beijing has wasted no time in expressing sympathy for the disaster. 

"I want to use today's opportunity to extend our deep condolences for the loss of lives in this disaster and to express our sincere sympathy to the Japanese people," Chinese Premier Wen Jiabao said at the end of his annual news conference in Beijing on Monday.

"China is also a country that is prone to earthquake disasters and we fully empathise with how the Japanese people feel now... The Chinese rescue team arrived in Japan yesterday and we have provided relief supplies to Japan. We will continue to provide further necessary aid to Japan in accordance with their needs."

South Korea said a 102-member rescue team departed for Japan on Monday aboard three air force C-130 planes. An advance team of five South Korean rescue workers and two search dogs have been in Japan since Saturday.

Indonesia, hit by a huge earthquake and tsunami in 2004 that killed more than 165,000 in Sumatra and more than 225,000 around the Indian Ocean, said it was committed to send aid to Japan and was awaiting a go-ahead from Tokyo.

"We are ready to help, and we have offered them. We are discussing what Japan needs now and ways to send it, but our aid, including medical and relief team are at the ready," said foreign ministry spokeswoman Kusuma Habir.

Nuclear emergency

The US is also sharing its expertise in dealing with Japan's nuclear emergency.

But US warships and planes helping the relief efforts have moved away from Japan's country's Pacific coast temporarily because of low-level radiation from a stricken nuclear power plant in Fukushima, the US Navy said.

Carney said a US disaster response team sent to Tokyo included "people with nuclear expertise from the Departments of Energy and Health and Human Services as well the Nuclear Regulatory Commission (NRC)".

"The NRC members are experts in boiling water nuclear reactors and are available to assist their Japanese counterparts," he said.

The southern Afghan city of Kandahar announced it was donating $50,000 to the "brothers and sisters" of Japan.

"I know $50,000 is not a lot of money for a country like Japan, but it is a show of appreciation from the Kandahar people," city Mayor Ghulam Haidar Hamidi told Reuters.

At least a dozen countries have now deployed rescue teams the United Nations said, but conditions in the worst-hit areas remained extremely difficult.

"Rescue and relief operations are being hampered by continuous aftershocks, tsunami alerts and fires. Many areas along the northeast coast remain isolated and unreachable," a United Nations statement said.

Britain has sent fire brigade search and rescue specialists and equipment including heavy lifting and cutting equipment, and said it would send nuclear physicists if requested.

Russia's state nuclear corporation, Rosatom, said it had offered to help in responding to the problems at Japanese nuclear plants if necessary. Russia sent 75 rescuers on Sunday to work in quake-affected areas, the Emergencies Ministry said.

Teams from Medecins Sans Frontieres (Doctors Without Borders) have reached Sendai, one of the cities nearest the quake epicentre. The group said the medical situation seemed under control, but there was little electricity and no water supply. People needed food, blankets, and water.

Almost 2 million households were without power in the freezing north, the government said. There were about 1.4 million without running water. – Reuters