A second earthquake of magnitude 6.4 has struck southern Japan in the same area affected by another quake earlier.
At least five people have been seriously injured.
Police say they have received reports of collapsed houses and people possibly trapped inside.
Keisukei Urata, an official at Uki city, said he was driving home when the first quake struck in the nearby town of Mashiki in Kumamoto prefecture.
He said he saw some walls around houses collapsing.
Parts of the ceiling at Uki City Hall collapsed, windows were broken and cabinets fell to the ground.
Kasumi Nakamura, an official in the village of Nishihara near the epicentre, said the rattling started modestly and grew violent, lasting about 30 seconds.
"Papers, files, flower vases and everything fell on the floor," he told NHK TV. He said there were aftershocks.
One aftershock measuring 5.7 struck about 40 minutes later, according to Japan's Meteorological Agency.
The US Geological Survey put the quake's preliminary magnitude at 6 and said it was 14 miles deep. It did not expect major damage.
Footage on NHK showed a sign hanging from a ceiling shaking violently.
File cabinets rattled, books, files and papers rained down to the floor, and one employee appeared to have fallen off a chair, while others slid underneath their desks to protect their heads.