A magnitude-6.6 earthquake hit off the eastern coast of Japan on Sunday, rattling buildings across a broad swath of the country, including the crowded capital.

There were no reports of casualties, with only light damage to structures near the epicentre, according to local officials.

The quake hit at 5:08 p.m. local time and was felt most strongly in central Fukushima prefecture, about 210 kilometres northeast of Tokyo, according to the Japan Meteorological Agency.

"It was fairly strong, but didn't knock over anything in the office," said Ken Yoshida, a town official in Naraha, one of the hardest-hit areas. He said an earthen wall in town was partially toppled.

The earthquake was centred about 80 kilometres off the eastern coast at a depth of about 40 kilometres, the meteorological agency said.

The government said there was no danger of a tsunami, although slight changes to ocean levels were a possibility in some areas.

It was strong enough to gently sway large buildings in Tokyo and was felt across a broad stretch of Japan's main Honshu and northern Hokkaido islands.

Japan's early warning system predicted the earthquake just before it hit, with public broadcaster NHK interrupting a sumo match to warn residents to take cover.

Japan is one of the world's most earthquake-prone countries. In 1995, a magnitude-7.2 quake in the western port city of Kobe killed 6,400 people.