Toll in Japan flood disaster rises to 179: Government

Map showing parts of Japan that have been swamped by heavy rains and flooding. (AFP/Laurence CHU)

Search-and-rescue operations are continuing after floods and landslides caused by the rains, and local media said several dozen people were still missing in Japan's deadliest weather-related disaster in over three decades.

Torrential rain unleashed floods and landslides in western Japan last week, bringing death and destruction, especially to neighbourhoods built decades ago near steep slopes. About 67 people are missing, the government said.

In the city of Kurashiki, the flooding engulfed entire districts at one point, forcing some people to their rooftops to wait for rescue.

Rescue workers were going door-to-door, looking for survivors - or victims - of the disaster.

"It's what we call a grid operation, where we are checking every single house to see if there are people still trapped inside them," an official with the local Okayama prefecture government told AFP.

"We know it's a race against time, we are trying as hard as we can."

NEW DANGERS FROM HEAT

It is Japan's deadliest weather-related disaster in more than three decades, and has sparked national grief.

On Monday, Prime Minister Shinzo Abe cancelled a four-stop foreign trip as the death toll rose, and he will visit Okayama on Wednesday.

Around 75,000 police, firemen and troops have been deployed in the search and rescue operation across parts of central and western Japan, top government spokesman Yoshihide Suga said, warning that hot weather posed new risks.

Thousands of people remain in shelters, and local authorities in some areas were offering drinking water and bathing services for those without their own supply.

Power had been restored to all but 3,500 households but more than 200,000 people remain without water under scorching sun, with temperatures hitting 33 Celsius in some of the hardest-hit areas, such as the city of Kurashiki.

"It will be over 35 Celsius in some areas ... Please be careful about heatstroke if you're doing reconstruction outdoors, and continue to be vigilant about landslides," Suga said.

The government said it would tap around US$20 million in reserve funds to provide aid to those affected by the disaster.

And even with the rains over, the risk of flooding remained, with the town of Fuchu in Hiroshima issuing a new evacuation order as a local river burst its banks.

"Driftwood and dirt has piled up ... and now the water has started overflowing from the river," a spokesman for the local fire department told AFP.

"We are on high alert," he added.

In Ehime prefecture, authorities said they were struggling to get emergency food and water to some cut-off areas.

"We are sending them by boat and air routes," said Yoshinobu Katsuura, a spokesman for the prefecture's disaster management department.

"It will take a lot of time to see devastated areas recover."