A strong 6.0-magnitude earthquake hit western Japan early Saturday but there was no risk of a tsunami, the country's meteorological agency reported.
The quake struck at 5:33 am (2033 GMT on Friday) near Awaji island in the Seto Inland Sea southwest of the city of Kobe at a relatively shallow depth of 10 kilometres (six miles), the agency said.
The US Geological Survey also measured the tremor at 6.0 but at a even shallower depth of five kilometres.
Local train services were suspended to check safety, while Kansai airport in Osaka Bay was temporarily closed, Japan's public broadcaster NHK said.
At least two people were injured and the wall of a house was damaged, NHK said.
The epicentre was close to the 1995 Kobe quake that struck the port city, killing more than 6,000 people.
Kansai Electric Power said there was nothing untoward at its Oi nuclear power plant, currently the only one in Japan with reactors online.
"Our operation has continued as we haven't monitored any abnormality, but we are still checking if there is any damage to the facilities," a plant official said.
Japan is regularly hit by powerful earthquakes and has largely adapted its infrastructure to tremors that can cause widespread damage in other, less developed countries.
However, a huge undersea quake with a magnitude of 9.0 in March 2011 sent a towering tsunami into the northeast of the country, devastating coastal communities and killing nearly 19,000 people.
It also sparked the world's worst atomic accident in a generation when waves knocked out the cooling systems at Fukushima nuclear plant.
Japan turned off its 50 reactors in the wake of the Fukushima disaster but the two at the Oi plant resumed operations due to fears of a power shortage.