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TOKYO — Japan was reeling from its most powerful typhoon in 25 years when it was struck by another natural disaster early Thursday: a powerful earthquake that killed at least nine people and left nearly 3 million households without power.

The quake struck the northernmost island of Hokkaido at 3:08 a.m. Thursday (2:08 p.m. ET Wednesday), triggering landslides that left dozens missing.

The government said it was sending 20,000 search-and-rescue personnel to the region.

The quake triggered a landslide in Atsuma, Japan. Jiji Press / AFP - Getty Images

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The Japan Meteorological Agency said the quake's magnitude was 6.7, while the U.S. Geological Survey said 6.6. No tsunami warning was issued.

In Atsuma, a town just three miles from the epicenter, a massive landslide on the side of a mountain crushed homes beneath. At least four people there were confirmed killed, with around 30 missing, and more than 195 people injured, according to Chief Cabinet Secretary Yoshihide Suga.

Suga said the quake also killed one person in the regional capital of Sapporo, which has a population of 1.9 million, after a mudslide hit a road and half-buried several cars.

The earthquake came when Japan was already dealing with the effects of Typhoon Jebi, which struck two days earlier. The strongest to hit the country in 25 years, the storm has killed at least 11 people.

On Thursday, video on NHK national television showed the moment the quake struck Muroran, with its camera violently shaking and all city lights going out a moment later.

Elsewhere, aerial video showed slashes of brown earth on many heavily forested mountains, evidence of crushed homes, farm buildings and roads buried by avalanches of mud, logs and other debris.

Hiroshige Seko, Japan's economy, trade and industry minister, told reporters that the extensive power loss was caused by an emergency shutdown of the main thermal power plant that supplies half the electricity to Hokkaido.

A mud-covered car sits in a destroyed street after a powerful earthquake in Sapporo, Japan, on Thursday. Jiji Press / EPA

Three reactors at the Tomari nuclear plant were running on backup generators after they lost external power because of the island-wide blackouts, Japan's Nuclear Regulation Authority said.

Spent fuel in storage pools was safely cooled on backup power that can last for a week, the agency said.

Arata Yamamoto reported from Tokyo, and Alexander Smith from London.