An earthquake with a preliminary magnitude of 6.7 and a number of aftershocks rocked Japan's Hokkaido prefecture early Thursday, leaving multiple houses buried by landslides.
Rescue work is underway to search for the missing.
According to the Japan Meteorological Agency (JMA), the major temblor was centered in the Hokkaido prefecture at 3:08 a.m. local time Thursday (1808 GMT Wednesday), with the epicenter at a latitude of 42.7 degrees north and a longitude of 142.0 degrees east and at depth of 40 km.
The earthquake was logged upper 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 at 6:11 a.m. local time (2111 GMT Wednesday).
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.
Local 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 as of 7:00 a.m. local time (2200 GMT Wednesday), according to local firefighters.
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 as of 8:00 a.m. local time (2300 GMT Wednesday), 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 with no water supply.
Telephone service 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 local reports.
The Japanese central government has set up a liaison unit at the crisis management center of the prime minister's office to gather information on the quake.
It said some 25,000 personnels of the Japanese Self-Defense Forces will be dispatched to the quake-stricken areas for rescue and relief operations at the request of the governor of Hokkaido.
Japan's weather agency warned that earthquakes with a similar magnitude might again hit the quake-struck region in the following week.