Three people were killed in Saturday's powerful earthquake in northern Japan, an official said.
A hospital official said a 48-year-old construction worker on a dam project died after being hit by falling rocks in the city of Oshu.
Another 65 people were injured across Japan, according to the disaster management authority, while media reports put the figure above 100.
The government earlier said a 55-year-old man died when he was hit by a landslide while fishing and that a 60-year-old man died after running out of his home in fright and getting hit by a truck.
At least 12 people are also missing after the earthquake, which registered 7.2 on the Richter scale and was followed by nearly 100 aftershocks.
A small amount of radioactive water leaked at a storage facility at a nuclear power plant after the earthquake in Japan but there should be no concern to the public, the operator said.
Tokyo Electric Power Co said that 14.8 litres of water came out of a pool in which radioactive equipment is stored at the Fukushima Number Two Reactor in northern Fukushima prefecture.
"But the radiation level of the water is far below the level that could potentially affect the environment," a company spokesman said, adding that the reactor itself continued operation.
Nuclear power has been controversial in Japan in part due to the dangers of the archipelago's frequent earthquakes.
In July last year, a powerful earthquake in Niigata prefecture northwest of Japan caused a fire and a minor leak from the world's biggest power plant, Kashiwazaki-Kariwa, also run by Tokyo Electric.
No one was injured in the incident, but the government went so far as to invite in international inspectors to prove to the public that there were no health risks.
The giant power plant remains shut down for checks, causing major financial losses for Tokyo Electric, the world's largest private power company.
Japan endures 20 per cent of the world's major earthquakes but has been trying to step up its reliance on nuclear power as Asia's largest economy has virtually no natural energy resources.
Nuclear power currently accounts for roughly one-third of Japan's energy needs, the second highest ratio among the Group of Eight major economies after France.