Seven people were killed, over 900 people were injured in a magnitude 6.8 earthquake which rocked Niigata prefecture of central western Japan and surrounding areas on Monday morning.

The death toll of the 10:13 a.m. (0113 GMT) quake rose to seven late in the day. All victims were from the most heavily hit city of Kashiwazaki in Niigata. They were in their 70s or 80s.

According to Kyodo News, over 900 were injured in the quake Niigata, Nagano and other prefectures. Many suffered bone fractures, some of whom were seriously injured.

The Chinese Embassy in Japan said there has been no report of casualties of Chinese people in Japan.

The quake lead to waves up to 20 centimeters and destroyed 780 houses, leading about 10,000 people in Niigata to evacuate as a series of aftershocks followed.

An aftershock measuring 5.6 on the Richter scale jolted the area again at 15:37 p.m. (0637 GMT), among more than a dozen minor tremors, the Japan Meteorological Agency said. It also warned that more strong aftershocks are expected within the week.

Four of the seven nuclear reactors at Tokyo Electric Power Co.'s Kashiwazaki-Kariwa nuclear power station automatically shut down after sensing the strong quake. According to the operator, water with radioactive material was found leaking from the No. 6 nuclear reactor.

Besides, an electric transformer caught fire at the No. 3 reactor of the nuclear plant. The fire was brought under control around noon.

A two-car local train in Kashiwazaki station was derailed due to the strong quake. A 17-carriage cargo train was also derailed in a tunnel. No casualties were reported as to the two cases.

Most offices and schools were closed as Monday was a national holiday of Japan.

The epicenter of the major quake was around 17 kilometers below seabed in waters off Niigata prefecture, the agency said.

The quake also caused power failures in over 50,000 homes in Niigata and Nagano. East Japan Railway Co. halted bullet train services on the Tohoku, Joetsu and Nagano Shinkansen lines.

Several parts of highway in Niigata were also closed after the quake. Niigata airport shut down its runways immediately after the quake to check for damage.

The government has set up an emergency management center to handle the quake. Prime Minister Shinzo Abe, who rushed to Kashiwazaki, Niigata, in a helicopter in the afternoon, said that the government would do its best to reconstruct and restore the infrastructures as soon as possible. Some 450 Self-Defense Forces personnel were dispatched to the disaster area.

The quake measured upper 6 on the Japanese seismic intensity scale of 7 in Kashiwazaki and Kariwa in Niigata and Iizuna in Nagano, lower 6 in Joetsu and Nagaoka in Niigata, and upper 5 in Iiyama in Nagano. The earthquake also affected nearby prefectures including Ishikawa, Yamagata, Tochigi, Saitama, Fukushima and others.

In October 2004, a major earthquake hit Niigata prefecture, killing 67 people and injuring over 4,800.