A string of powerful earthquakes rocked northwestern Japan on Saturday evening, killing at least 18 people and injuring more than 1,000.

The quakes triggered massive power outages, scattered fires and caused severe damage to houses, bridges, highways and tunnels, according to several Japanese media outlets.

Analysts said they expected the death toll to rise given the number of people missing. The first and strongest of the quakes measured a magnitude 6.8 and hit at 5:56 p.m. near the city of Ojiya, 160 miles northwest of Tokyo, according to Japan's Meteorological Agency.

Over the next several hours, at least a half-dozen tremors and aftershocks were reported, including two quakes with magnitudes of 6.2 and 5.9.

The series of quakes derailed a bullet train, although there were no reported injuries related to the accident. Officials told Japanese media that 250,000 homes in the affected area were without power, sewage and water mains had burst, and gas and telephone services were down.

The quake came as Japan was still cleaning up from its deadliest typhoon in more than a decade. Typhoon Tokage blew across Japan on Wednesday, leaving 79 dead and more than a dozen others missing.

"I've never felt anything like it before," Yoichi Kato, the owner of a 7-11 store in Kashiwazaki, about 12 miles west of the epicenter, told the Associated Press after the quake. "It was so strong; I was too surprised to be scared."

-- Anthony Faiola