SENDAI, Japan (AFP) - Japan on Sunday committed 100,000 troops to help earthquake and tsunami survivors as the world rallied behind the disaster-stricken nation and a US aircraft carrier arrived off the shattered coast.

The deployment, ordered by Prime Minister Naoto Kan, doubles the number of troops already on the ground, after the massive scale of the devastation wrought by the twin disasters emerged.

"I ask for utmost efforts to save the lives of as many people as possible," Kan told a meeting of the government's emergency disaster headquarters, Kyodo News reported.

Defence Minister Toshimi Kitazawa said the 100,000 troops -- about 40 percent of the armed forces -- would be fully deployed within two days.

"There are so many people who are still isolated and waiting for assistance. This reality is very stark," he said.

His comments came amid bleak warnings of a surge in the death toll. The police chief of Miyagi prefecture, the region hardest hit by Friday's natural disasters, on Sunday told reporters the toll there will exceed 10,000.

"There is no doubt that the number will reach the 10,000-level," said Naoto Takeuchi, quoted by state broadcaster NHK, referring to just his own prefecture.

Elsewhere police and military reported finding groups of hundreds of bodies along the tsunami-battered coastline, including more than 200 found in one location on Sunday.

Offers of help poured in from across the world including from traditional rivals China, who despite last year's territorial row with Japan, sent condolences from Premier Wen Jiabao and Foreign Minister Yang Jiechi and a team of 15 rescuers.

Japan's foreign ministry said 69 nations or regions and five international aid organisations had offered their assistance as of Sunday morning.

Among them was New Zealand, which suffered its own earthquake tragedy last month in the city of Christchurch.

A 66-strong Japanese team which has spent more than two weeks scouring the rubble in Christchurch also rushed home to confront the unfolding tragedy.

Search and rescue teams and sniffer dogs arrived from Germany and Switzerland, and rescuers from Britain and France have been dispatched.

Japan has asked the US aircraft carrier Ronald Reagan for help to refuel its helicopters and transport troops to affected areas.

A 150-member rescue team of the US Agency for International Development was due later Sunday to join inland operations. The team includes 12 dogs trained to find victims trapped under rubble and about 150 tonnes of rescue equipment.

Australia, South Korea and Singapore also pledged dogs and search and rescue teams. Australia has offered field hospitals and disaster victim identification teams, said Foreign Minister Kevin Rudd.

Canberra also offered to send nuclear specialists to help manage the threat posed by a damaged nuclear power station, Rudd added.

Two experts from the US Nuclear Regulatory Commission were headed for Japan, where tsunami and earthquake damage to one nuclear plant led to the evacuation of tens of thousands of people amid fears of a possible meltdown.

The 8.9-magnitude tremor unleashed a 10-metre (33-foot) tsunami that raced over towns and farming land, engulfing everything in its path as it turned into a deadly churn of water, mud and debris.

The top government spokesman said at least 1,000 people were believed to have lost their lives and police said more than 215,000 people remain huddled in emergency shelters.

In Rikuzentakata, in Iwate prefecture north of Miyagi, scores of corpses were found Sunday morning under rubble, Kyodo News reported without giving a precise figure.

About 5,000 houses in the city had been submerged, it said, and only 5,900 out of its population of about 23,000 had taken shelter when the disaster struck.