TOKYO, April 21 (Xinhua) -- An earthquake measured 5.9 on the Richter scale rocked southwestern Japan islands in Kagoshima prefecture early Saturday, the Japan Meteorological Agency said.

    No tsunami warnings were issued as to the 4:38 a.m. local time (1938 GMT, Friday) quake. There were no immediate reports of casualties or damage.

    Its epicenter was 40 km underground at 27.5 degrees northern latitude and 128.5 degrees eastern longitude, the agency said, adding that the quake also affected parts of Okinawa prefecture.