TOKYO (REUTERS) - Japan's southern Okinawa island and a chain of neighbouring islands were shaken on Monday (Sept 26) by an earthquake with a preliminary magnitude of 5.7, but no tsunami warning was issued and there were no immediate reports of damage or injury.

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.

On March 11, 2011, the north-east coast was struck by a magnitude 9 earthquake, the strongest quake in Japan on record, and a massive tsunami. Those events triggered the world's worst nuclear crisis since Chernobyl a quarter of a century earlier.