A strong quake, registering 6.3 on the Richter scale, jolted the northern island of Hokkaido at 7:03 pm (1003 GMT) but there were no fears of tidal waves, the Japan Meteorological Agency said.

Earlier at 6:04 pm (0904 GMT), a minor quake shook Niigata with a magnitude of 3.9, the agency said.

There were no immediate reports of casualties or damage resulting from the quakes.

Meanwhile, the Niigata quake death toll reached 40 as a 78-year-old agricultural machine dealer was confirmed to have died of heart failure at a hospital after suffering a lack of sleep while sheltering in a car.

The National Police Agency said at least 3,180 people had been injured in the series of quakes which started on October 23, with one measuring 6.8 on the Richter scale.

It was the deadliest earthquake-caused disaster to hit Japan since 1995, when 6,433 people were killed in the western city of Kobe by a quake registering 7.3.

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