Rescue work is underway to search for the missing.
According to the Japan Meteorological Agency (JMA), the major temblor was centred in the Hokkaido prefecture at 3.08 a.m. (Japan time) with the epicentre at a latitude of 42.7 degrees north and a longitude of 142.0 degrees east, and at depth of 40 km, Xinhua reported.
The earthquake was logged above 6 in some areas of Hokkaido prefecture on the Japanese seismic intensity scale which peaks at 7.
Dozens of aftershock followed, including one with a preliminary magnitude of 5.4 that hit the prefecture three hours later.
Japan's Nuclear Regulation Authority said the Tomari nuclear power plant operated by Hokkaido Electric Power Co.'s, had lost an external power source, and a spent fuel pool of its reactors was currently being cooled by an emergency power supply system.
The nuclear watchdog said no abnormality had been confirmed in radiation levels around the plant.
The JMA said there might be a slight sea-level change in Japan's coastal areas as a result of the magnitude 6.7 quake.
Police said they had received multiple reports of injuries as a result of the quake, including an 82-year-old man who was found with no vital signs after falling down the stairs but was later recovered.
In Sapporo, capital city of Hokkaido, 53 people were reported injured.
A number of houses in the quake-stricken areas collapsed, with rescue work under way for those possibly buried under the houses, according to local officials.
In Atsuma, at least 16 people were missing after eight households were buried by landslides, according to public broadcaster NHK.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
