At least nine people have been killed and nearly 1,000 injured after a 6.2-magnitude earthquake knocked down houses and destroyed roads in southwestern Japan.

The tremor struck 11km east of Kumamoto on Thursday, according to the US Geological Survey, and strong aftershocks continued to shake the area around the city on Friday.

More than 40,000 people were evacuated to schools and community centres, some spending the night outside after the first quake hit around 9:30pm local time.

Roads cracked, houses crumbled and tiles fell from the roof of Kumamoto Castle in the centre of the city.

The damage and calls for help are concentrated in the town of Mashiki, about 1,300km southwest of Tokyo [Kyodo News]

More than 3,000 troops, police and firefighters were dispatched to the area from around Japan, and Shinzo Abe, prime minister, said more would be sent if needed.

Rescuers were concentrating their searches in Mashiki, near the epicentre of the quake where eight of the nine deaths occurred.

Footage from public broadcaster NHK showed firefighters tackling a blaze in a building in Mashiki, a town of about 34,000 people.

About 16,500 households in and around Mashiki were without electricity, according to Kyushu Electric Power Company.

 

There were no irregularities at three nuclear plants on the southern major island of Kyushu and nearby Shikoku, the Nuclear Regulation Authority said.

The plant is 130km south of Kumamoto. The operator restarted the reactors last year, the first two units under updated regulations.

In March 2011, a 9.0-magnitude earthquake led to a devastating tsunami that killed 18,000 people along Japan's northeast coast.

The wave struck the Fukushima nuclear plant, causing a major radiation leakage.  

More than 100,000 displaced people are still unable to return to their homes near the nuclear plant because of the contamination.

Japanese media showed residents, some of them wrapped in blankets, huddling in a parking lot [Kyodo News]

Nearly 1,000 people were injured in Thursday's earthquake and the aftershocks on Friday [Reuters]

Source: Agencies