Hundreds were injured in September's earthquake in Hokkaido

No casualties have been reported from the quake, which took place at 1006 local time (0106 GMT) under the seabed off the coast of Fukushima prefecture.

It measured 6.8, enough to cause considerable damage in populated areas.

It is not clear whether the quake is related to similar seismic activity in the area in May in which 100 people were injured.

Japan is one of the world's most earthquake prone countries.

It lies across four slabs of rock, known as tectonic plates, which, when they rub against each other, cause earthquakes.

Several hundred people were injured in a quake on the northern island of Hokkaido at the end of September.

Perhaps the most notorious was in January 1995, when more than 6,000 people died in the western city of Kobe.