Rescuers in a Japanese town hit by a deadly landslide climbed onto cracked roofs and searched cars thrown onto engulfed buildings on Sunday, as more rain lashed the area.

Two people have been confirmed dead after the disaster at the hot-spring resort of Atami in central Japan, with 10 people rescued and around 20 still missing, a local government official said.

Torrents of mud crashed through part of the town on Saturday morning following days of heavy rain, sweeping away hillside homes and turning residential areas into a quagmire that stretched down to the nearby coast.

"We resumed rescue operations early in the morning with some 1,000 rescuers, including 140 troops," said a Shizuoka prefecture official.

A survivor told local media he had heard a "horrible sound" and fled to higher ground as emergency workers urged people to evacuate.

Around 2,800 homes in Atami have been left without power, the Tokyo Electric Power Company said on Saturday.

The town, around 90 kilometers southwest of Tokyo, saw rainfall of 313 mm (millimeters) in just 48 hours to Saturday - higher than the average monthly total for July of 242.5mm, according to public broadcaster NHK.

Much of Japan is currently in its annual rainy season, which lasts several weeks and often causes floods and landslides, prompting local authorities to issue evacuation orders.

Prime Minister Yoshihide Suga had on Saturday warned residents to stay alert for further landslides triggered by the rain.

The highest evacuation alert, which urges people "to secure safety urgently", was issued after the disaster in Atami, which has 20,000 households, reports said.

Residents in many other cities in Shizuoka have also been ordered to evacuate.

In 2018, more than 200 people died as devastating floods inundated western Japan.