Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

By The Associated Press and Arata Yamamoto

At least nine people were killed Thursday night and hundreds of others were injured, at least 53 of them seriously, as a magnitude-6.5 earthquake knocked down houses and buckled roads in southern Japan, police and fire officials said.

All of the dead — four dead and five women — and nearly all of the at least 900 people who were injured were in Kumamoto city and the town of Mashiki in Kumamoto prefecture, police said, according to national broadcaster NHK. More than 44,000 people in the prefecture had fled to shelters overnight, fire officials told NBC News.

Cars move past fallen walls after an earthquake Thursday in the town of Mashiki in Kumamoto in southern Japan. AP

The quake struck at 9:26 p.m. (8:26 a.m. ET) at a depth of 7 miles near Kumamoto city on the island of Kyushu, the Japan Meteorological Agency said. There was no tsunami risk.

"The shaking was so violent I couldn't stand still," said Hironobu Kosaki, a Kumamoto police official.

Japan's chief cabinet secretary, Yoshihide Suga, said at least 19 houses collapsed, and hundreds of calls came in reporting building damage and people buried under debris or trapped inside. Nearly half of the 650-foot-long wall surrounding Kumamoto Castle was damaged, NHK reported.

"Because of the night darkness, the extent of damage is still unclear," he said.

The damage and calls for help are concentrated in the town of Mashiki, about 800 miles southwest of Tokyo, Japan's Fire and Disaster Management Agency said.

One of the victims in Mashiki died after being pulled from some rubble, and the other was killed in a fire, Matsushita said. A third person rescued from under a collapsed building is in a state of heart and lung failure.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

Matsushita said rescue operations were repeatedly disrupted by aftershocks.

Related: Secretary Kerry Visits Hiroshima, Site of First Nuclear Attack

"There was a ka-boom, and the whole house shook violently sideways," Takahiko Morita, a Mashiki resident, said in a telephone interview with Japanese broadcaster NHK. "Furniture and bookshelves fell down, and books were all over the floor."

Morita said that some houses and walls collapsed in his neighborhood and that water supply had been cut off.

Residents take shelter outside the town hall of Mashiki near Kumamoto in southern Japan after an earthquake Thursday. Ryosuke Uematsu / AP

Dozens of people evacuated their homes and gathered outside Mashiki town hall, sitting on tarps well after midnight. Some wrapped blankets around their shoulders against the springtime chill.

Prime Minister Shinzo Abe told reporters that the government has mobilized police, firefighters and self-defense troops for the rescue operation.

"We'll carry out relief operations through the night," he said.

Suga said there were no abnormalities at nearby nuclear facilities. The epicenter was 74 miles northeast of Kyushu Electric Power Co.'s Sendai nuclear plant, the only one operating in the country.

Most of Japan's nuclear reactors remain offline following the meltdowns at the Tokyo Electric Power Co.'s Fukushima plant in 2011 after a magnitude-9.0 earthquake triggered a huge tsunami.

Television video showed fires breaking out in some places, with firefighters battling an orange blaze.

Keisukei Urata, an official in nearby Uki city who was driving home when the quake struck, told NHK that parts of the ceiling at Uki City Hall collapsed, windows broke and cabinets fell to the ground.

Kasumi Nakamura, an official in the village of Nishihara, 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.

There were multiple aftershocks, the largest one with a preliminary magnitude of 6.4 shortly after midnight (11 a.m. ET), according to the Japan Meteorological Agency.

The U.S. Geological Survey measured the initial quake's preliminary magnitude at 6.2. It upgraded its damage assessment to red, meaning extensive damage is probable and the disaster is likely widespread.

Video from an NHK bureau in the area showed books, files and papers raining down to the floor. One employee appeared to have fallen off a chair, while others slid under their desks to protect their heads.