TOKYO, JAPAN (AFP) - A moderate, 5.5-magnitude offshore earthquake hit southern Japan on Wednesday, the US Geological Survey said, although there were no immediate reports of casualties or damage and no tsunami alert was issued.

The quake struck at 4:03 am (3.03 am Singapore time) 142 kilometres southwest of the country's remote, Bonin Islands, which lie some 1,000 km south of the capital, Tokyo, at a depth of 86 km, the US agency said.

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