A powerful magnitude-6.5 earthquake has hit Japan's south-western island of Kyushu, collapsing homes, sparking fires, leaving at least nine people dead and injuring hundreds, government officials say, as the scramble continues to rescue people feared trapped in the rubble.

Key points: A series of quakes and tremors hit Japan

A series of quakes and tremors hit Japan Reports of collapsed buildings, injuries, and thousands without electricity and gas

Reports of collapsed buildings, injuries, and thousands without electricity and gas Officials say that nuclear facilities were safe, but are checking for damages

Tens of thousands of people reportedly fled their homes and television footage showed damaged buildings, buckled roads and lumps of broken concrete in the streets.

The Kyodo news agency said some 44,400 people had been evacuated and more than 100 aftershocks had been recorded since the quake.

The Government said it had confirmed at least 761 people had been injured, at least 44 seriously.

Officials say a "significant" number of houses have been destroyed. ( AFP: Jiji Press )

Some 1,600 military personnel were joined by nearly 2,000 police officers and more than 1,300 firefighters to help in the search and rescue efforts, Government spokesman Yoshihide Suga said.

As the death toll rose during the night, an eight-month-old baby girl was pulled from the rubble alive and unharmed, NHK reported.

"As far as we can tell from infrared images from a police helicopter, there appears to be a significant number of houses destroyed or half-collapsed," Disaster Minister Taro Kono said.

"There are fears the number of injured could rise."

The quake struck at 9:26pm (local time) in Kumamoto at a relatively shallow depth of 10 kilometres, the Japan Meteorological Agency said, adding there was no danger of a tsunami.

Sorry, this video has expired Huge quake hits Japan's Kumamoto

"I felt quite strong jolts, which I had never experienced before," Shunsuke Sakuragi, a prefectural official in Kumamoto, said.

"People were shocked but I have not seen any extreme confusion in the city.

"We also received information indicating a few people were under collapsed houses."

Hours after the main earthquake another tremor measuring magnitude 6.4 hit the same region just after midnight on Friday, according to the Japan Meteorological Agency.

The US Geological Survey measured the first quake at 6.2, and put the second quake at 5.4 — another smaller aftershock followed.

Aftershocks were likely to continue for about a week, it said.

Evacuees gather in front of the town office building after escaping homes when the earthquake struck. ( Reuters: Kyodo )

Japanese media reported that some 16,000 households in the area were without electricity and 38,000 homes had no gas supplies in Kumamoto.

Prime Minister Shinzo Abe convened an emergency response meeting of emergency officials at his office to plot a response.

"We are doing everything to avoid a second disaster because of aftershocks, and to offer the necessary help to those affected," he told reporters on Friday morning.

Jiji media reported that bullet train services were halted on the island, while NHK said one of the trains had derailed though it was not carrying passengers at the time.

Houses collapsed, nuclear facilities checked

Authorities are working to free people trapped under rubble after the powerful quake. ( Reuters: Kyodo )

NHK reported that some buildings had collapsed in the town of Mashiki in Kumamoto with people possibly trapped underneath.

"The apartment building I live in is now tilting. Everything fell down inside. It's a mess," a Mashiki resident said on NHK.

Rescue workers use a stretcher to carry a woman who was rescued from a collapsed house in Mashiki town. ( Reuters: Kyodo )

The broadcaster showed what appeared to be a house in flames as firefighters attempted to douse it with water — it reported a total of three fires sparked by the quakes.

Meanwhile, Japan's two sole operating nuclear reactors, located on Kyushu, were functioning normally, an official at the Sendai plant operated by Kyushu Electric Power said, though he said technicians were checking for damage.

"We are doing our best for emergency disaster measures by prioritising efforts to save and rescue victims," Mr Suga said.

"I ask people in the disaster zone to act calmly and help each other."

Japan sits at the junction of four tectonic plates and experiences around 20 per cent of the world's most powerful earthquakes.

But rigid building codes and strict enforcement mean even powerful tremors frequently do little damage.

A massive undersea quake that hit on March 11, 2011, sent a tsunami barrelling into Japan's north-east coast, leaving about 18,500 people dead or missing, and sending several reactors into meltdown at the Fukushima nuclear plant in the worst atomic accident in a generation.

Map Map showing the epicentre of the earthquake.

AFP/Reuters