A man makes his way through split road after a strong earthquake hit Nagaoka city, Niigata prefecture, northwestern Japan, Monday, July 16, 2007. A 6.8-magnitude earthquake rocked Japan's northwest coast on Monday, killing at least two people. The quake injured more than 200 people, flattened dozens of wooden buildings. (AP Photo/Mainichi Shimbun) ** JAPAN OUT NO SALES, ONLINE OUT, CREDIT MANDATORY **

KASHIWAZAKI, Japan — A strong earthquake struck northwestern Japan today, destroying hundreds of homes, buckling roads and bridges and causing a fire at a nuclear power plant. At least six people were killed and hundreds were injured.

The quake hit the region shortly after 10 a.m. local time and was centered off the coast of Niigata state. Buildings swayed 160 miles away in Tokyo. The hardest-hit area appeared to be Kashiwazaki, a city of about 90,000 in Niigata

Japan's Meteorological Agency measured the quake at a 6.8 magnitude. The U.S. Geological Survey, which monitors quakes around the world, said it registered 6.7.

Flames and billows of black smoke poured from the Kashiwazaki nuclear plant, which automatically shut down during the quake. The fire, in an electrical transformer, was put out about two hours later and there was no release of radioactivity or damage to the reactors, said Motoyasu Tamaki, a Tokyo Electric Power Co. official.

Tsunami warnings were issued along the coast of Niigata but later lifted.

A series of smaller aftershocks rattled the area, including one with a 5.8 magnitude. The Meteorological Agency warned that the aftershocks could continue for a week.

The quake hit on Marine Day, a national holiday in Japan, when most people would have been at home.

Four women and two men — all either in their 70s or 80s — died after buildings collapsed on them, according to the National Police Agency in Tokyo.

National broadcaster NHK reported more than 700 people were hurt.

Nearly 300 homes in Kashiwazaki — a city known mainly for its fishing industry — were destroyed and some 2,000 people evacuated, officials said.

The quake buckled seaside roads and bridges, and left fissures three feet wide in the ground along the coast.

A ceiling collapsed in a gym in Kashiwazaki where about 200 people had gathered for a badminton tournament, and one person was hurt. The quake also knocked a train car off the rails while it was stopped at a station. No one was injured.

Several bullet train services linking Tokyo to northern and northwestern Japan were suspended. More than 60,000 homes were without water and 34,000 without gas.