Police and the coastguard in Japan carried out large-scale searches Wednesday for the bodies of more than 2,500 people still missing two-and-a-half years since the quake-tsunami and nuclear disaster it spawned.

Some 90 searchers combed coastlines and water off the Onahama district of Fukushima prefecture, roughly 50 kilometres (30 miles) south of the crippled Fukushima atomic power plant.

"If you imagine the feelings of the family members of missing individuals, it's very saddening," said Hiroshi Kuno, police chief of Iwaki Higashi police station.

"We want to find the missing individuals or their belongings," he told local media.

Similar searches were being carried out all along a vast stretch of the northeast of Japan.

The vast bulk of the coastline, along with rivers running into the sea, have been searched several times before, but officials say they are trying to ensure no spot has been overlooked.

The prefectures of Iwate, Miyagi and Fukushima were hit directly by the 9.0-magnitude earthquake and killer tsunami on March 11, 2011.

A total of 15,883 people have been confirmed killed by the natural disasters, many in Miyagi, which bore the brunt of the destruction.

The bodies of a further 2,654 people have never been recovered, but all are assumed dead.

Giant waves knocked out cooling systems at the Fukushima Daiichi nuclear plant, which went through meltdowns and explosions that contaminated a vast farming region.

No one died as a direct result of the nuclear crisis. However, the government has added a further 2,688 deaths to the total toll for the triple disaster, counting as victims those who died due to stress or other complications associated with evacuation.

The already improbable search for the missing is becoming more difficult as months go by and officials privately accept that many bodies will never be found.

Nearly 300,000 people who fled their homes due to the tsunami and the nuclear disaster still remain in temporary housing, recent figures show.

Many young people and families have left the region to start new lives.