July 16 (Bloomberg) -- An earthquake struck central Japan near Niigata, toppling houses, causing a fire at a nuclear power plant and suspending bullet train services. Seven people were killed and more than 800 were injured, NHK television reported.

The magnitude 6.8 quake, centered off the Japan Sea coast, triggered a tsunami warning that was later lifted, the country's meteorological agency said on its Web site. The quake's epicenter was about 250 kilometers (155 miles) northwest of Tokyo, where buildings swayed for several minutes around 10:15 a.m.

NHK showed images of houses with collapsed roofs, cracked highways and a train carriage derailed at a station in the coastal city of Kashiwazaki.

Japan yesterday began cleaning up after being battered for three days by Typhoon Man-Yi, which caused three deaths, injured scores of people and disrupted air and rail transport. Many offices are shut today for Marine Day, a national holiday.

Radioactive water leaked from a nuclear reactor at the Kashiwazaki-Kariwa power plant in Niigata because of the earthquake, Tokyo Electric Power Co. told the Kyodo news service. The leak occurred at the plant's No. 6 reactor, which had automatically shut down when the tremors began, the company said.

As of noon local time, 21,541 households in Niigata prefecture were without power, the Trade Ministry said in an e- mailed statement. Supply of natural gas, a typical cooking fuel in Japan, was cut to 34,000 houses, the statement said.

Abe Visits Zone

Prime Minister Shinzo Abe cut short an election campaign stop in the southern city of Nagasaki to fly to Kashiwazaki, the area hardest hit by the quake, Kyodo News reported. The government earlier set up an emergency task force and sent Kensei Mizote, minister in charge of disaster management, to inspect quake-hit areas, it said.

East Japan Railway Co., the country's largest train operator, halted part of its Shinkansen bullet train services, said Takahiro Kikuchi, a company spokesman.

Services on the Joetsu line between the Echigo Yuzawa resort area and Niigata on the Japan Sea coast remained suspended as of 3 p.m., while trains resumed service between Tokyo and Echigo Yuzawa. Service was also restored on the Tohoku and Nagano bullet train lines, which connect Tokyo with northern Japan and the central prefecture of Nagano.

Local trains operated by JR East, as the company is known, derailed at Kashiwazaki station and in the Yoneyama Tunnel in Niigata, Kikuchi said. No one was injured, he said.

Mobile Service Disrupted

The earthquake damaged 93 base stations operated by Softbank Corp., owner of Japan's third-largest wireless carrier. The damage disrupted part of the company's mobile phone services in Niigata and Nagano, said Katsuhide Furuya, a Softbank Mobile Corp. spokesman.

The Niigata area was hit by a quake in October 2004 that killed at least 33 people and injured 2,900. It forced East Japan Railway to shut a section of the Joetsu bullet train line for two months and damaged a semiconductor plant in the area operated by Sanyo Electric Co.

Sanyo, which halted the plant today, will resume production tomorrow, Sanyo spokesman Akihiko Oiwa said via phone. ``There is no damage to the building and no workers were injured,'' he said.

Matsushita Electric Industrial Co., the world's largest consumer-electronics maker, had no serious damage at its plants, spokesman Akira Kadota said. Its Niigata factory makes facsimile and copying machines, according to the company's Web site.

Japan, one of the world's most earthquake-prone countries, is located in a zone where the Eurasian, Pacific, Philippine and North American tectonic plates meet and occasionally shift, causing earthquakes. Quakes of magnitude 5 and more can cause considerable damage.

To contact the reporters on this story: Mariko Yasu in Tokyo at myasu@bloomberg.net; Drew Gibson in Tokyo at dgibson2@bloomberg.net.

Last Updated: July 16, 2007 10:35 EDT