An earthquake measuring 6.9 magnitude on the Richter scale on Saturday rocked Okinawa Prefecture and its vicinity in southern Japan, said the Japan Meteorological Agency.

The focus of the quake, which occurred at 5:31 a.m. local time (2031 GMT Friday), was located some 10 km under the sea 50 km east off Naha, capital of Okinawa, said the agency.

Two people, both female and aged 74 and 66, were reportedly slightly injured in the earthquake, local government reported.

The agency issued an warning of up to 2-meter high tsunami seismic waves for coastal regions of the main Okinawa island soon after the quake, but soon downgraded it to an advisory at about 6: 30 a.m., and later lifted it at around 7 a.m.

Small waves of up to around 10 centimeters reached Nanjo city on the island and Minamidaito village just before 6 a.m., the agency said.