Map locating the powerful 6.6 magnitude quake that hit the northern Japanese island of Hokkaido.
The magnitude 6.7 quake early Thursday unleashed scores of landslides that buried homes in avalanches of soil, rock and timber.
At least eight people have been killed and about 40 are missing, say local media reports.
Of the 18 people confirmed or presumed dead, 14 were from Atsuma.
Aerial footage showed dozens of landslides exposing barren hillsides near the town of Atsuma in southern Hokkaido, with mounds of red earth and toppled trees piled at the edge of green fields.
"This is shocking. I was always walking on this street and I had never imagined this road could collapse in such a way", said resident Sumi Noriyuki.
"It came in four big jerks - boom! boom! boom! boom!" one unidentified woman told NHK. "Before we knew it our house was bent and we couldn't open the door".
"Please give your sympathy to people who spent a dark night in fear, and do everything you can to restore electricity as soon as possible", Prime Minister Shinzo Abe told a cabinet meeting to discuss the quake.
Hokkaido Electric said 2.95 million homes had lost power after the quake.
It was the first time since the utility was established in 1951 that had happened.
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Some 1.6 million residents across Hokkaido remain without power. Buses and trains were also halted. Abe's Liberal Democratic Party begins a leadership contest on Friday but said there would be no campaigning through to Sunday. Officials said at least 366 were injured, five seriously, and about 30 were unaccounted for after the magnitude 6.7 quake jolted people from their beds at 3.08am. Police directed traffic because signal lights were out while drink-vending machines, ubiquitous in Japan, and most ATMs were not working.
Some 28 people were unaccounted for in the town, Atsuma mayor Shoichiro Miyasaka said.
The risk of housing collapses and landslides had increased, he said, urging residents "to pay full attention to seismic activity and rainfall and not to go into risky areas".
Rescue workers have continued to search for survivors after a powerful quake triggered landslides on Japan's northern island of Hokkaido. Mandatory credit Kyodo/via REUTERS.
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. Debris and water could be seen on the terminal floors.
The natural disaster comes on the heels of a deadly typhoon lashing the west of Japan over the past few days.
But a football friendly between Japan and Chile in Sapporo planned on Friday was scrapped due to the transport and power chaos in Hokkaido.
The quake struck as Japan was recovering from a typhoon which hit the Western part of the country on Tuesday, killing 11 people, injuring hundreds and closed the regional airport. That was followed by a heat wave that reached a record 41.1 Celsius and led to the deaths of at least 80 people.
Manufacturers were still affected by power outages.