Rescue efforts continue as thousands of soldiers work to help people stranded after torrential rains hit southwestern Japan for a second day on Thursday. The rains have resulted in the death of three people, with 100,000 urged to evacuate their homes.
Heavy rain warnings were in effect for much of the southern main island of Kyushu after Typhoon Nanmadol slammed Japan on Tuesday.
Parts of Fukuoka prefecture, on the island of Kyushu, were hit by 556 mm (22 inches) of rain in the 40 hours to 4 pm (0700 GMT) on Thursday, about 1.6 times the amount that usually falls in the whole of July, the weather agency said.
At least three people had been killed, three were in "cardiopulmonary arrest" and eight were injured, public broadcaster NHK reported.
About 300 people were stranded, mostly in their homes, cut off by floods or landslides.
"We are in an extremely serious situation," Deputy Prime Minister Taro Aso said, warning of the danger of collapsing hillsides, adding "many people are still missing".
"Since daybreak today, we have mobilised 7,800 people from police, fire authorities and the Self-Defence Forces to do our utmost in searching and rescuing the affected," Chief Cabinet Secretary Yoshihide Suga told a news conference.
About 250 people had been rescued, but there were some areas where the rescue teams had yet to reach, he said. "There are about 20 people who are unaccounted for" in the region as of Thursday afternoon, Suga said.
One man who was dug up from a mudslide was pronounced dead in neighbouring Oita prefecture, according to the Fire and Disaster Management Agency.
In one of the worst-hit towns, Asakura in Fukuoka, one man managed a narrow escape when a landslide crushed his home on a steep mountain slope, NHK said.
Nearly 600,000 people were ordered or advised to evacuate in Fukuoka, but only a fraction of them did, in part because the heavy rain worsened during the night.
Only about 1,800 people had sought refuge in schools and other public facilities as of early Thursday, according to the prefecture's disaster management website.
In Oita, more than 270,000 people were asked to evacuate.
"Soil has been loosened in these regions because of the heavy rain ... Strict vigilance should be maintained," an agency official told reporters.
Fukuoka and Oita were experiencing unprecedented amounts of rain, causing rivers to burst their banks, sweeping away roads and houses, and destroying schools, said Japan's Meteorological Agency.
Many broken trees washed down from mountains were floating in flooded fields or blocking roads.
Homes were without electricity, trains were suspended and parts of highways closed. Classes at dozens of schools, including those used as shelters, were cancelled on Thursday.
Downpours will likely continue through Friday, the agency said.