More than 1000 soldiers, firefighters and police have waded through a giant mudslide that ripped through a resort town southwest of Tokyo, killing at least two people and leaving more than 110 unaccounted for as it swept away houses and cars.

Prime Minister Yoshihide Suga said on Sunday 19 people had been rescued, and 130 homes and other buildings were damaged in Atami.

Local media reported two women found in “cardiac and respiratory arrest” were later pronounced dead while the whereabouts of dozens of people were unknown after the incident.

The masses of mud flattened everything in their path – electricity pylons, cars, entire residential buildings that collapsed like a house of cards, and streets that sank into the mud.

“The earth slid to the front of the shop. It sounded like an excavator smashing a house,” an employee of a glass studio in Atami said.

At an evacuation centre, Yuka Komatsu, 47, told the Asahi newspaper she narrowly escaped the mudslide after seeing a nearby apartment building being hit.

She grabbed her mother and jumped into her car. In the rearview mirror, she saw muddy water swelling and coming from behind as it washed down broken trees and rocks.

“I wonder what happened to our house?” she said.

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Professor Motoyuki Ushiyama of the Shizuoka University Centre for Integrated Research and Education of Natural Hazards told Kyodo news agency the mudslide was estimated to be travelling at about 40 kilometres per hour.

Japanese television broadcast footage of citizens capturing the moment on Twitter when the black wave of mud suddenly burst from a hillside through several houses taking everything with it.

The mudslide covered a wide area and slid close to the coast. The two victims with no signs of life were found near a harbour.

Rescue workers were searching for the missing with the support of soldiers who had been called in.

On Sunday afternoon local time, troops, firefighters and other rescue workers, backed by three coast guard ships, were working to clear the mud from the streets of Atami and reach those believed to be trapped or carried away.

They were barely visible in the rainfall and thick fog except for the their hard hats. Six military drones were being flown to help in the search.

The mudslide on July 3 crashed down a mountainside into rows of houses following heavy rains that began several days ago. Bystanders, their gasps of horror audible, caught the scene on mobile phone video.

Witnesses said they heard a giant roar and then watched helplessly as homes were gobbled up by the muddy waves.

Like many others, Mariko Hattori, an interpreter who lives a short walk away from where the tsunami-like torrent of mud struck, at first didn’t know what happened.

“The first things I noticed were lots of emergency vehicles. I didn’t know what happened at first,” she said. “Then I was frightened when I saw the footage.”

The area of Atami where the mudslide struck, Izusan, is a seaside resort about 100 kilometres southwest of Tokyo. It’s known for hot springs, a shrine and shopping streets.

More rain on the way

The meteorological agency in Tokyo also warned of heavy rains in large areas of the country for the next few days.

Residents in other places along the country’s Pacific coast were warned to take shelter from rising rivers, flooding and possible landslides.

In the past 10 years, according to official data, there have been an average of almost 1500 landslides per year in the mountainous island country – almost twice as many as in the previous decade.

Experts ascribe this to increased rainfall due to climate change.

-with AAP