A magnitude-6.6 earthquake struck south-western Japan early Monday, the Meteorological Agency said.
No casualties or damage were reported and no tsunami warning was issued.
The quake jolted the region at 5:11 am with its seismic centre off the north-western coast of the main Okinawa island, at a depth of 120 kilometres, the agency said.
The quake registered intensity 4 on the Japanese seismic scale of 7 in several areas of Okinawa, 1,600 kilometres south-west of Tokyo.