TOKYO -- A 5.6-magnitude offshore earthquake shook south western Japan on Sunday, but there were no immediate reports of casualties or damage, officials said.

The meteorological agency said there was no risk of a tsunami from the quake, which hit at 6:36 p.m. (0936 GMT).

The epicenter was about 30 kilometers (19 miles) below sea level in the Pacific Ocean off south western Kyushu Island, some 850 kilometers (530 miles) from Tokyo, according to the agency.

Around 20 percent of the world's most powerful earthquakes strike Japan.