An earthquake with a preliminary magnitude of 6.4 hit southern Japan late on Wednesday, said the Japan Meteorological Agency, without issuing a tsunami warning.
The epicenter was the Bungo Channel, a strait separating the Japanese islands of Kyushu and Shikoku, the agency said.
Ehime and Kochi prefectures were hit by the quake with an intensity of 6 on Japan's 1-7 scale, the JMA said.
Some water pipes burst, but no major damage has been reported, local media said.
Shikoku Electric Power's Ikata nuclear plant in Ehime Prefecture, where one reactor is in operation, reported no irregularities, Japan's government spokesperson Yoshimasa Hayashi told reporters.
Hayashi also warned of a chance of other earthquakes with lower six on the Japanese seismic scale.
