HONG KONG, Aug. 7 (Xinhua) -- A moderate earthquake measuring 5.7 on the Richter scale occurred northwest of Ryukyu Islands, Japan, at 8:05 a.m. Tuesday (0005 GMT), the Hong Kong Observatory reported.

    The epicenter was initially determined to be 27.4 degrees north latitude and 126.7 degrees east longitude, about 170 km northwest of Naha, the Hong Kong Observatory said in a bulletin released Thursday.

    There was no immediate report of casualties or damage.