One person died in a landslide and hundreds of thousands of people have been urged to evacuate their homes in southwestern Japan as forecasters today warned of the "heaviest rain ever" in the region.
A 77-year-old woman was confirmed dead in a landslide that hit her home overnight in rural Fukuoka, the local fire department told AFP.
Her husband was recovered conscious and taken to hospital.
Three people were also missing after a landslide in Karatsu City, in Saga prefecture, which neighbours Fukuoka, local authorities said.
By late Monday morning, over 420,000 people in Fukuoka prefecture and neighbouring Oita were under a top-level evacuation warning, which informs people: "Your life is in danger, you need to take action immediately".
More than 2 million people across Fukuoka, Hiroshima, Saga, Yamaguchi and Oita prefectures were under a lower-level warning, urging them to evacuate if they are in hazardous areas.
Japan has a five-level evacuation order, but people cannot be compelled to leave their homes.
The Japan Meteorological Agency said the heavy downpours risked flooding and landslides across the Fukuoka and Oita regions.
"A special heavy rain warning has been issued for municipalities in Fukuoka Prefecture. This is the heaviest rain ever experienced" by the region, Satoshi Sugimoto of JMA's forecast division told reporters.
"There is a very high possibility that some kind of disaster has already occurred... The situation is such that lives are in danger and safety must be secured," he added.
Footage on national broadcaster NHK showed a gash in the hillside above a home in Karatsu City that had partly collapsed into a river, with many of its traditional roof tiles smashed or sliding off.
Images from elsewhere showed surging rivers washing over bridges that normally sit well above the waterline, and floodwater turning local streets into streams.
The prime minister's office said a task force had been established to coordinate a response to the rains.
"We have received reports that several rivers have flooded... and that landslides have occurred in various parts" of the country, top government spokesman Hirokazu Matsuno told reporters.
"The government is doing its best to get a complete picture of the damage and taking measures under a policy of 'people's lives first,'" he added.
The downpour caused travel disruption, including the temporary stoppage of bullet train service between western Hiroshima and Fukuoka, operator JR West said.
And thousands of homes across western Japan have lost power, Matsuno said.
Japan is currently in its annual rainy season, which often brings heavy downpours, and sometimes results in flooding and landslides, as well as casualties.
Scientists say climate change is intensifying the risk of heavy rain in Japan and elsewhere, because a warmer atmosphere holds more water.
The weather agency said it had already been raining for over a week in the region.
"The area is very wet due to intermittent rainfall for over a week," Yoshiyuki Toyoguchi, land ministry official in charge of rivers, told reporters.
"Even with a little rain, river levels tend to rise quickly, which will increase risk of flooding."
Landslides are a particular risk in Japan during heavy rains, because homes are often built on plains at the bottom of hillsides in the mountainous country.
In 2021, rain triggered a devastating landslide in the central resort town of Atami that killed 27 people.
And in 2018, floods and landslides killed more than 200 people in western Japan during the rainy season.