Intense heat and water shortages raised fears of disease outbreaks in flood-hit western Japan on Thursday as the death toll from the worst weather disaster in 36 years neared 200.

More than 200,000 households had no water a week after torrential rains caused floods and set off landslides across western Japan, bringing death and destruction to decades-old communities built on mountain slopes and flood plains.

The death toll rose to 195, with several dozen people still missing, the government said on Thursday.

With daily temperatures above 30C and high humidity, life in school gymnasiums and other evacuation centres, where families spread out on mats on the floors, began to take a toll.

Television footage showed one elderly woman trying to sleep by kneeling with her upper body on the seat of a folding chair, arms over her eyes to keep out the light.

With few portable fans in the evacuation centres, many survivors tried to cool themselves with paper fans.

The limited water supply meant that people are not getting enough fluids and in danger of suffering from heatstroke, authorities said. People are also reluctant to use what water they do have to wash their hands, raising fears of epidemics.

"Without water, we can't really clean anything up. We can't wash anything," one man told NHK television.

Heavy rain leads to flooding and landslides in Japan Show all 15 1 /15 Heavy rain leads to flooding and landslides in Japan Heavy rain leads to flooding and landslides in Japan People await resuce in Kurashiki, Okayama prefecture AP Heavy rain leads to flooding and landslides in Japan A car stands on its nose in Okayama prefecture as flooding hits Japan Getty Heavy rain leads to flooding and landslides in Japan A rescue helicopter is on the scene of a landslide in Iwakuni, Yamaguchi prefecture AP Heavy rain leads to flooding and landslides in Japan An emergency crew attends to a train that has been derailed by a tree on the tracks. Heavy rain has caused landslides in Saga prefecture AFP/Getty Heavy rain leads to flooding and landslides in Japan Kurashiki, Okayama prefecture AFP/Getty Heavy rain leads to flooding and landslides in Japan A car is trapped in mud flows in Saka, Hiroshima prefecture AFP/Getty Heavy rain leads to flooding and landslides in Japan Kurashiki, Okayama prefecture AFP/Getty Heavy rain leads to flooding and landslides in Japan Rescue teams transport people from the Mabi Memorial Hospital in Kurashiki, Okayama prefecture AFP/Getty Heavy rain leads to flooding and landslides in Japan Kurashiki, Okayama prefecture AFP/Getty Heavy rain leads to flooding and landslides in Japan Soldiers search for victims in Kurashiki, Okayama prefecture AFP/Getty Heavy rain leads to flooding and landslides in Japan A road is damaged in Kurashiki, Okayama prefecture AP Heavy rain leads to flooding and landslides in Japan Rescue teams attend to inpatients, staff and residents at the Mabi Memorial Hospital in Kurashiki, Okayama prefecture EPA Heavy rain leads to flooding and landslides in Japan Kurashiki, Okayama prefecture EPA Heavy rain leads to flooding and landslides in Japan Police clear debris in Kumano, Hiroshima prefecture AFP/Getty Heavy rain leads to flooding and landslides in Japan Residents take shelter in an evacuation centre in Kurashiki, Okayama prefecture AFP/Getty

The government has sent water trucks to the disaster area, but supplies remain limited.

More than 70,000 military, police and firefighters toiled through the debris in a grim search for the missing.

Some teams shovelled dirt into sacks and piled the bags into trucks. Others used diggers and chainsaws to work through landslides and splintered buildings.

Many areas were buried deep in mud that smelled like sewage and had hardened in the heat, making the search more difficult.

Disasters set off by torrential rains have become more frequent in Japan, perhaps due to global warming, experts say. Dozens of people died after similar rains caused flooding around the same time last year.

"It's an undeniable fact that this sort of disaster due to torrential, unprecedented rain is becoming more frequent in recent years," chief cabinet secretary Yoshihide Suga said at a news conference in Tokyo.

"Preserving the lives and peaceful existence of our citizens is the government's biggest duty. We recognise that there's a need to look into steps we can take to reduce the damage from disasters like this even a little bit," he added.