A series of powerful earthquakes and aftershocks rattled northern Japan on Saturday, killing at least 16 people and reportedly injuring more than 900 as buildings crumbled, a bullet train derailed and roadways were torn apart.

At least four people were missing Saturday night, the government said. Throughout the region, electric, gas and telephone services were knocked out and water and sewage mains burst.

The quakes — the most powerful recorded as magnitude-6.8 — were spread over several hours and centered on Ojiya (search), about 160 miles northwest of Tokyo. Still, buildings swayed in the Japanese capital.

"I've never felt anything like it before," said Yoichi Kato, the owner of a 7-11 store in Kashiwazaki (search), about 12 miles west of the epicenter. "It was so strong, I was too surprised to be scared."

The quake knocked bottles and food off the convenience store's shelves, but otherwise caused his shop limited damage, Kato said.

The first quake hit at 5:56 p.m. and was centered about 12 miles beneath the surface, the Meteorological Agency said. At least six more tremors hit over the following hours, including quakes of magnitude 6.2 and 5.9, the agency said.

The second floor of a Jusco nationwide supermarket chain store was smashed.

"There were 300 customers inside when the earthquake hit, and everyone tried to grab something nearby to keep from being knocked off their feet," said Reiko Takahashi, the store's manager as she stood guard to prevent looting or possible injuries. "Several people were hurt by glass shards and falling debris."

Teams were dispatched to assess damage and aid residents but darkness and buckled roads hampered their efforts, officials said. Eleven military helicopters fanned out to check the damage and help with rescue operations, the agency said.

The quakes were centered in relatively rural areas. The government has estimated that some 7,000 people would die if such a powerful quake hit the Tokyo area.

The victims included a 34-year-old man who was struck by a falling wall as he fled his home in Tokamachi and a 55-year-old man buried by his concrete garage wall.

Takejiro Hoshino, 75, lost his 12-year-old grandson when their house collapsed. "I got out and then we all went back to try to save the others, but it was too late," Hoshino said.

Two others were stuck in a house buried by a landslide in Ojiya, and four people were missing in Nagaoka city after two homes collapsed, NHK said. Telephone service to the area was cut and the deaths could not be confirmed with local officials.

Nearly 50 people were injured by flying glass or items that fell from shelves in Tokamachi and Ojiya cities, according to media reports.

Japan's Fire and Disaster Management Agency said early Sunday that 16 people had died and that 350 were injured. Kyodo News agency, however, put the toll of injured at some 900. Doctors were treating the wounded in hallways and reception areas.

"There were four to five jolts so strong we couldn't keep standing without grabbing something like a desk," Toshio Kasuga, an official in the town of Takayanagi, told Kyodo News. "I saw some landslides on a hillside on my way to the office."

Elsewhere, sewage and water mains burst, gas and telephone services were down, and about 280,000 homes lost power, officials told Japanese media.

A major nuclear power plant operated by Tokyo Electric in Kashiwazaki was operating normally.

Across Niigata state, 61,000 people were evacuated to emergency shelters. In Ojiya, 5,290 people took refuge at 50 different evacuation centers, while many more were spending the night in their cars, said city official Mikio Oya.

Television footage from Ojiya showed overturned cars scattered about a 33-foot crater carved out of an uprooted highway.

The jolt triggered an automatic safety device that temporarily halted train services, according to media reports. Railway officials said at least two trains, including a bullet train, derailed and some cars tipped over in Niigata prefecture, but nobody appeared to be hurt.

The temblors came just days after Japan's deadliest typhoon in more than a decade, which left 79 dead and a dozen others missing.

Typhoon Tokage ripped through the country with high waves and rapid mudslides, demolishing homes and flooding dozens of communities in western Japan before losing power and disappearing over the Pacific Ocean.

Japan, which rests atop several tectonic plates, is among the world's most earthquake-prone countries. A magnitude 6 quake can cause widespread damage to homes and other buildings if centered on a heavily populated area.