A magnitude 6.4 earthquake struck a group of Japanese islands south of Tokyo at 4:54 p.m. local time, the U.S. Geological Survey said on its Web site.

The quake hit near the island of Iwoto, formerly known as Iwo Jima, 1,005 kilometers (603 miles) south of Tokyo and was 14 kilometers deep, the USGS said. The magnitude was initially put at 6.6.

There were no immediate reports of casualties or damage. There's no danger of a destructive tsunami from the quake, although small sea-level changes are possible, the Japan Meteorological Agency said on its Web site.

Japan lies in a zone where the Eurasian, Pacific and Philippine plates meet and is one of the world's most earthquake-prone countries. Earthquakes of magnitude 5 or more can cause considerable damage, depending on their depth.