An earthquake measuring about 7.3 on the Richter scale has shaken western Japan, the second strong quake to hit the area in five hours.
There were no immediate reports of damage or injuries, but tsunamis measuring up to one metre were expected to hit the Pacific coast.
Earlier, there were no reports of serious damage when an earthquake measuring 6.9 on the Richter scale hit the same area.
Two people were slightly injured in the city of Kyoto, although some of the strongest tremors were felt in the area of Nara, the ancient capital of Japan where there are many temples.
