Japan issued a tsunami alert after a 7.1-magnitude earthquake hit the country’s southwest on Tuesday, knocking out power to thousands of households.
The tremor at 4.27pm local time on the island of Kyushu also measured at the highest possible level seven on Japan’s own Shindo scale of shaking, the Japan Meteorological Agency said.
The tsunami could measure up to one metre (three feet), the agency said.
Broadcaster NHK said waves of up to that level might already have been recorded.
No immediate abnormalities were recorded at nuclear power plants, the Nuclear Regulation Authority said.
About 45,000 households and facilities have no power in the Kumamoto region, according to local utility Kyushu Electric Power.