Japan (AP) - A 6.3-magnitude earthquake has struck in the Pacific Ocean off southern Japan. The U.S. Geological Survey says the quake struck Monday night 200 miles southwest of Naha on Okinawa island in southern Japan. Local time was 10:28 p.m. (1328 GMT) at the epicenter, which is around the Ryukyu Islands. It was at a depth of 22 miles. The Japan Meteorological Agency issued an alert for a mild tsunami for nearby islands. There was no immediate report of any damage or injuries.