TOKYO — A powerful earthquake struck off the northern Japanese coast early today, injuring nearly 100 people, triggering landslides and cutting power to thousands of people, officials said.

Japan's Meteorological Agency said there was no danger of a tsunami from the temblor, which had a preliminary magnitude of 6.8. It struck shortly after midnight about 65 miles underground and centered just off the coast of Iwate, 280 miles northeast of Tokyo.

The injured people were mainly suffering from cuts and bruises from broken glasses and falling objects, and none of the injuries was life threatening, said National Police Agency official on condition of anonymity, citing department policy.

The earthquake caused strong shaking for up to 40 seconds in large parts of northern Japan, official said.

"Everything has fallen off the shelves, scattered all over the floor," grocery store owner Tomio Kudo told national broadcaster NHK from the town of Hirono, where the shaking was most violent. "Even a big refrigerator has moved about 30 centimeters (1 foot)."

There were no immediate reports of any problems at the nearest nuclear power plant, which continued operations, according to local media reports.

But Japan's "bullet" super-express trains were stopped in some areas, according to operator East Japan Railway Co.

The earthquake also triggered landslides at several locations, the police agency official said.

Disaster Minister Shinya Izumi told reporters that the earthquake caused a blackout in wide areas in the region, leaving about 6,700 homes without electricity. Izumi said a team of officials from the ministry were assessing the extent of damage.

Police said some of the more serious injuries included: a woman in Hirono and another in nearby Aomori City who each broke a leg falling down stairs; another woman in Aomori City who broke her hip as she fled out a window; and a 66-year-old woman in Miyagi prefecture who broke her arm falling from a bed.

Japan is one of the world's most earthquake-prone countries.

A 6.8 magnitude earthquake is capable of causing serious, widespread damage. Last month, a 7.2-magnitude earthquake struck sparsely populated rural areas in northern Japan, killing at least 12 people, leaving 10 others missing and injuring more than 300.

Meteorological Agency official Takashi Yokota warned of possible aftershocks from Thursday's quake.