Police and military reported finding groups of hundreds of bodies at locations along the shattered coastline, including more than 200 found at a new site on Sunday.

JAPAN is desperately trying to bring an overheating nuclear reactor under control as the full horror of its quake-tsunami disaster emerged on the ravaged northeast coast with thousands feared dead.

An explosion at the Fukushima atomic plant blew off the roof and walls around one of its reactors on Saturday, triggering fears of a meltdown a day after the biggest ever quake recorded in Japan.

The 8.9-magnitude tremor unleashed a monster 10-metre tsunami that raced over towns and farming land, destroying all before it and leaving the coast a swampy wasteland.

In the small port town of Minamisanriku alone some 10,000 people were unaccounted for - more than half the population - public broadcaster NHK reported.

Police and military reported finding groups of hundreds of bodies at locations along the shattered coastline, including more than 200 found at a new site on Sunday.