By Elaine Lies, REUTERS UK

TOKYO (Reuters) - A strong earthquake jolted northwestern Japan on Monday, injuring dozens of people, destroying some houses and causing a fire at a nuclear power plant, Japanese media and officials said. “I was on the street, and there was strong sideways shaking. I couldn’t remain standing. One wall has collapsed,” gasoline station worker Hiroki Takahashi told NHK in Kashiwazaki City, near the focus of the quake, where TV broadcasters said at least 12 people where trapped under collapsed houses.

TV pictures showed black smoke billowing from a electrical transformer building at Kashiwazaki Kariwa nuclear power plant in Niigata prefecture, near the epicentre some 250 km (155 miles) northwest of Tokyo. Buildings swayed in Tokyo, some trains were stopped and nuclear power reactors in the Niigata area were shut down for checks but there was no radiation leakage reported.

The 10:13 a.m. (0113 GMT) quake with a preliminary magnitude of 6.6 was centred around 60 km (37 miles) southwest of Niigata. The focus of the quake was some 10 km below the earth’s surface, Japan’s Meteorological Agency said. “There were ambulances and fire trucks running so there seems to be injuries,” Masae Yanai told public broadcaster NHK from Kashiwazaki.

“Gas seems to have leaked in some places. Electricity is fine, but I can’t go inside,” he added.
Tsunami warning sirens sounded along affected stretches of the Sea of Japan, with a surge of up to about 50 cm (20 inches) predicted, but the warning was later withdrawn.
Monday is a holiday in Japan so financial markets were closed. Bullet train services were halted and NHK said there were power outages and some highways had been closed.

Niigata was the site of an October 2004 earthquake with a magnitude of 6.8 which killed 65 people and injured more than 3,000. That was the deadliest quake since a magnitude 7.3 tremor hit the city of Kobe in 1995, killing more than 6,400.

(Additional reporting by Tokyo bureau)