Japan is continuing to be hit by aftershocks following Friday's earthquake and tsunami that are believed to have killed at least 1,800 people.
Earlier a strong quake measuring 6.2 hit off its eastern coast causing buildings to sway in the capital Tokyo.
Japan has been rattled by more than 150 aftershocks since Friday's massive 8.9 magnitude quake - the largest on record in the country.
Kyodo news agency said the number of dead or unaccounted is expected to exceed 1,800.
Around 10,000 people are unaccounted for in the port of Minamisanriku - half of the town's population.
The confirmed death toll from the combined disasters stands at 688, while at least 1,000 people have been injured.
The Japanese military said 300 to 400 bodies were found in Rikuzentakata, where a wave barrelled into the densely-packed town.
Police found 200 to 300 bodies on beaches near Sendai but were still assessing the devastation in the northeastern port of one million people.
nternational rescue teams are en-route to Japan.
Britain has sent a 59-strong search and rescue team with two rescue dogs, a medical support unit and 11 tons of specialist rescue equipment including heavy lifting and cutting gear.
US aircraft carrier USS Ronald Reagan has arrived off the coast of Japan to provide logistical support for Japanese forces.
Japan has asked it to refuel its helicopters and help transport its troops to affected areas.
A 144-member rescue team of the US Agency for International Development is also due at Misawa, northern Japan, later to join inland operations.
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