Rescuers work at a collapsed house after an earthquake in the town of Atsuma, Hokkaidoprefecture, Japan, on Sept. 6, 2018. (Xinhua/Deng Min)

SAPPORO, Japan, Sept. 6 (Xinhua) -- "I was woken up by cellphone alarms early in the morning, and then felt the building shaking strongly," said Wang, a Chinese tourist in the city of Date, some 100 kilometers from the epicenter when a powerful earthquake rocked northern Japanese island of Hokkaido early Thursday.

"I then opened the TV to watch news on the earthquake, but less than five minutes later, the electricity was off. I looked out from the hotel room window, and the whole city seemed to have blacked out," Wang later told Xinhua.

The earthquake, with a preliminary magnitude of 6.7, struck Hokkaido prefecture at 3:08 a.m. local time Thursday (1808 GMT Wednesday), and was followed by dozens of aftershocks.

The quake logged the maximum 7 on Japan's seismic intensity scale, marking the first time for Hokkaido since the seismic scale was revised in 1996, according to Japan's weather agency.

In the town of Atsuma, one of the areas hit hardest by the quake, Self-Defense Force personnel were seen searching for people missing, with hillsides laid bare and residential areas and farm lands engulfed by landslides.

"A senior man in his 80s has been buried under this collapsed house. We don't know whether we can rescue him," a Self-Defense Force personnel told Xinhua at one of such rescue sites.

As of Thursday night, at least nine people have been confirmed dead and more than 300 people have been injured due to the powerful quake.

Meanwhile, some 30 people remain missing, and thousands of people are taking refuge in emergency evacuation shelters that have been set up at more than 500 locations across the prefecture.

A sign reading "Service suspended due to power failure" is posted on the entrance of a convenience store after an earthquake in Date, Hokkaido, Japan, on Sept. 6, 2018. (Xinhua/Deng Min)

Complicating rescue efforts, Hokkaido Electric Power Company said that power is still out across the whole of Japan's northernmost prefecture and 2.95 million homes are without electricity in the aftermath of the powerful quake.

Authorities said that the massive power outage was caused due to the halt of a thermal power plant that produced nearly half of the prefecture's electricity.

The halt of the power plant destabilized the whole power supply system and some other thermal power plants were also forced to an emergency halt, they said.

In Sapporo, capital city of Hokkaido and famous for its beautiful night scene, streets and buildings were blacked out due to the power outage.

As traffic lights were out, local police had to guide the traffic by hand and passengers and drivers were called upon to be wary of traffic accidents.

Also due to the power outage, many hospitals in the prefecture were forced to turn off equipment and turn away patients.

Japanese Prime Minister Shinzo Abe said that the government will try its best to restore power for some one million households by Friday morning.

Japan's Economy, Trade, and Industry Minister Hiroshige Seko, for his part, said that it will probably take more than a week to restore full power across the prefecture.