Television footage showed torrents of muddy, debris-strewn water and flooded houses following "unprecedented" downpours
About 400,000 people were ordered or advised to leave their homes in southwest Japan Saturday as heavy rain pounded the area for a third day leaving 29 dead or missing, officials and media said.
The Japan Meteorological Agency warned of more landslides and floods on the main southern island of Kyushu as rainfall of up to 11 centimetres (4.3 inches) per hour was recorded Saturday.
Evacuation orders were issued to about 260,000 people in the north of the island where more rivers burst their banks, Kyushu's local media reported.
They were told to go to designated shelters such as schools and other public facilities.
Nearly 140,000 other people were advised to leave their homes to avoid possible disaster, according to officials contacted by AFP in the four affected prefectures in Kyushu.
Television footage showed torrents of muddy, debris-strewn water and flooded houses following what officials described as "unprecedented" downpours from a seasonal rain front.
Along the Yamakuni river in Oita prefecture, water levels were seen reaching the roof of a riverside drive-in restaurant before subsiding later.
In Fukuoka prefecture alone, 78,600 people were ordered to evacuate their homes as rivers overflowed in dozens of places and 181 landslides occurred, an official said.
About 820 houses were damaged and three bridges washed away, Fukuoka prefecture spokesman Hiroaki Aoki told AFP by telephone.
"Two men were rescued from landslides but their conditions were not immediately available. One woman was still trapped," he said. "I don't remember any flooding which stretched over such a wide area in our prefecture."
More than 75 centimetres of rain fell in 72 hours in the city of Aso, situated at the foot of a volcano in Kumamoto prefecture, the meteorological agency said.
The death toll remained at 20 overnight, with 19 of the fatalities from landslides and house collapses in and near Aso.
Nine people were missing, with two listed on Saturday after a 30-year-old man fell into a swelling river in his car in Oita and a 83-year-old woman was buried in a landslide in Fukuoka.