Rescuers using dogs, backhoes and shovels have been searching for survivors trapped in mud and debris from landslides triggered by a powerful earthquake in northern Japan.

At least 16 people were dead or presumed dead last night after scores of hillsides collapsed, burying homes on the country's northernmost main island of Hokkaido.

The magnitude 6.7 quake on Thursday unleashed scores of landslides that buried homes in avalanches of soil, rock and timber. In Atsuma, a town of about 4600 people, 26 were still unaccounted for.

The landslides ripped through some homes and buried others. Some residents interviewed by national broadcaster NHK described awakening to find their relatives and next-door neighbours gone.

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"The entire thing just collapsed," said one. "It's unbelievable."

Prime Minister Shinzo Abe said nearly half of the nearly 3 million households on the island had their power restored after a day of island-wide blackouts.

"The forecasts are for rain, and that could bring more landslides, so please continue to exercise extreme caution," he said.

Hokkaido is Japan's northern frontier and a major farming region with rugged mountain ranges and vast forests, and its people are accustomed to coping with long winters, isolation and other hardships.

It is sparsely populated compared to the rest of Japan, but disruptions were widespread. Many roads were closed and some were impassable.

In Sapporo, the regional capital and home to 1.9 million people, casualties were relatively light.

Economy, Trade and Industry Minister Hiroshige Seko said it would take at least a week to fully restore power to all communities due to damage at a thermal power plant at Tomato-Atsuma that supplies half of Hokkaido's electricity.

Japan has had a string of natural disasters in recent months. The quake came on the heels of Typhoon Jebi, the strongest to hit Japan in 25 years, which claimed 11 lives, lifted heavy trucks off their wheels and triggered major flooding in western Japan, and damaged the main airport near Osaka and Kobe. A prolonged heat wave in July was blamed for at least 116 deaths, with the temperature reaching 41.1C on July 23 in Kumagaya, about 65km northwest of Tokyo, the highest recorded anywhere in Japan in recent history. Unusually heavy rain in western Japan in July claimed 221 lives as landslides buried homes and rivers broke through embankments.

A magnitude 6.1 earthquake struck during the morning rush hour in the city of Osaka on June 18, killing five people and injuring more than 400 others.

- AP