An undersea earthquake with a preliminary magnitude of 6.2 shook northern Japan early Saturday, but there was no danger of a tsunami, the Meteorological Agency said. There were no immediate reports of damages or injuries.

The quake occurred shortly after 3:30 a.m. and was centered about 30 miles below the seabed off the coast of Miyagi prefecture, about 180 miles northeast of Tokyo, the agency said.

The temblor was felt most strongly in the city of Ishinomaki but also was felt across the nearby prefectures of Aomori, Iwate and Tochigi, the agency said.

Public broadcaster NHK said its office in Miyagi shook for several seconds but nothing broke or fell from shelves.

Japan is one of the world's most earthquake-prone countries because it sits atop four tectonic plates.

A 7.2-magnitude earthquake shook northeastern Japan in August, injuring at least 59 people, triggering landslides, damaging buildings and causing widespread power outages.