Dozens of people were still missing and four in critical condition as torrential rain that has killed 20 people pounds western and central Japan, according to local officials.
Intense rainfall triggered huge landslides and flash floods in Hiroshima, Okayama, Kyoto and other regions, while hampering rescue operations.
Local authorities said on Saturday a total of 20 people were killed in rain-related accidents, while public broadcaster NHK said the death toll had risen to 38 with 50 others unaccounted for.
The broadcaster also said that more than 1.6 million people had been ordered to evacuate from their homes.
Japan’s Prime Minister Shinzo Abe told his ministers to “make an all-out effort” to rescue victims, saying: “The situation is extremely serious.”
Japan’s Meteorological Agency retained special weather warnings for three prefectures in the main island of Honshu, down from five, and urged vigilance against landslides, rising rivers and strong winds amid what it called “historic” rains.
More rain forecasted
Although a weather front had settled between western and eastern Japan, there was a risk that heavy rains would continue as warm air flowed towards the front with already-saturated areas facing more rain on Sunday, the agency said.
In Motoyama, a town on Shikoku island about 600 km from Tokyo, 583 millimetres of rain fell between Friday and Saturday mornings.
Minako Sakurai, an agency official, told reporters heavy rain was expected to continue until Sunday in western and eastern Japan.
Abe ordered his ministers to “make an all-out effort” to rescue victims [Kyodo via Reuters]
Some areas have been hit by more than a metre of rainfall, according to the government.
In Hiroshima, the body of a man in his 60s was found near a bridge early Saturday and another man was killed when a mudslide struck his house, a local government official said.
A 52-year-old woman in Kyoto was found dead by a river on Friday, while in neighbouring Hyogo prefecture a construction worker was swept away by flood waters and died.
Television footage showed a wooden bridge being washed away in Hiroshima by a rain-swollen muddy river.
Rescue workers dug into the dirt as landslides crushed houses in the same region, while several people evacuated to their rooftops as floods swamped entire residential areas in part of the Okayama region.
Yoshihide Suga, chief cabinet secretary, said that about 48,000 troops, police and firefighters have been deployed for rescue operations.
Although Japan is among the most modernised of Asian nations, rural areas are hit hard by the rainy season each year, often resulting in casualties and heavy damage.