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 news agency reported.
Multiple houses were buried by landslides and rescue work is underway for those still missing, Japan's public broadcaster NHK said.
The earthquake was logged upper 6 in some areas of Hokkaido prefecture on the Japanese seismic intensity scale which peaks at 7.
It was the first time for a quake in Hokkaido to reach an intensity of upper 6 since the seismic scale was revised in 1996, the JMA noted.
Dozens of aftershock followed, including one with a preliminary magnitude of 5.4 that hit the prefecture three hours later.
The JMA has warned that earthquakes with a similar intensity could continue in the area for about a week.
Japan's Nuclear Regulation Authority said that the Tomari nuclear power plant operated by Hokkaido Electric Power Co.'s, had lost an external power source, and a spent fuel pool was currently being cooled by an emergency power supply system.
The nuclear watchdog said that no abnormalities had been observed 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.
A potentially lethal fire broke out at a petrochemical complex in Muroran and was later extinguished by firefighters.
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.
The quake has also triggered power blackouts across a wide area in Hokkaido affecting some 3 million households, and hundreds of thousands of households were reported as having no water supply.
Telephone services and television broadcasting in Sapporo were affected, and flights were cancelled at New Chitose Airport due to the power outage, and bullet train and local train services were also disrupted.
More than 1,300 public schools in the prefecture have decided to temporarily close and asked their students to stay at home, according to reports.
The Japanese government has set up a liaison unit at the crisis management center of the Prime Minister's office to gather more information on the quake.
It said that some 25,000 personnel from the Japanese Self-Defence Forces will be dispatched to the quake-stricken areas for rescue and relief operations at the request of the governor of Hokkaido.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
