Several people were killed and scores injured when a strong earthquake struck the area of Niigata in central Japan.
Worst hit was the city of Kashiwazaki, where a number of houses were damaged and older buildings were reduced to rubble.
Nearly 300 buildings in the city were destroyed and more than 7,000 people evacuated from their homes, officials said.
The region subsequently suffered several strong aftershocks.
Witnesses said the quake in Kashiwazaki was too strong for people to stand and went on for 20 seconds.
Elsewhere, the earthquake caused roads to buckle. A tsunami warning was briefly issued and 50cm-high waves were reported to have hit the coast.
At the Kashiwazaki nuclear plant, a fire broke out in an electricity transformer and a small amount of water containing radioactive material leaked into the sea, officials said.