A magnitude 7.3 quake hit Japan's southern island of Okinawa in the early hours of Saturday morning (local time) and Japan's weather agency issued a tsunami warning for up to two metres.
The US Geological Survey said the quake struck 84 km east of the city of Naha, about 1,600 km south of Tokyo.
The Japan Meteorological Agency put the magnitude at 6.9.
Earthquakes are common in Japan, one of the world's most seismically active areas. The country accounts for about 20% of the world's earthquakes of magnitude 6 or greater.
In October 2004, an earthquake with a magnitude of 6.8 struck the Niigata region in northern Japan, killing 65 people and injuring more than 3,000.
That was the deadliest quake since a magnitude 7.3 tremor hit the city of Kobe in 1995, killing more than 6,400.
