TOKYO (REUTERS) - A 6.4-magnitude earthquake struck off south Japan on Tuesday (Jan 8), the US Geological Survey said.

There were no immediate reports of damage or casualties. The quake was 39km deep and centred 116km south-south-east of Kagoshima.

Earthquakes are common in Japan, one of the world's most seismically active areas.

Japan accounts for about 20 per cent of the world's earthquakes of magnitude 6 or greater.