A strong earthquake with a preliminary magnitude of 6.6 struck off Japan's eastern coast Sunday, but the tremors that reached the archipelago could hardly be felt. There were no reports of injuries or damage.

The quake, which struck at 6:04 a.m., was centered about 20 km beneath the sea floor in the Pacific Ocean east of Tokyo, the Meteorological Agency said.

The quake was barely felt along the eastern seaboard of Honshu, the agency said.