Floods claimed their first victim in Japan and nearly 300,000 people were urged to flee their homes Saturday as a weather system that killed dozens on the Korean peninsula swept the country.

Local governments in the central province of Niigata and tsunami-hit Fukushima issued the guidance after the national weather agency urged citizens to be on maximum alert against more flooding and mudslides.

Helicopter footage on NHK showed bridges over the Shinano River in Niigata partially submerged, while trees and telephone polls had been knocked down.

Kamo City in Niigata was extensively flooded, with water submerging roads.

Forecasters warned that the rains could continue to be torrential after reaching 1,000 millimetres (40 inches) to date in Sanjo City, Niigata, 250 kilometres (155 miles) northwest of Tokyo, since they started Wednesday.

A total of 296,000 people had been asked to evacuate their homes by early Saturday, according to public broadcaster NHK, but no compulsory orders were issued despite muddy swollen rivers, broken dykes and flooded houses.

The same weather saw record rainfall kill at least 59 people in South Korea earlier this week, leaving thousands more homeless.

The first Japanese victim, Eiichi Murayama, 67, was confirmed dead in Tokamachi City, in Niigata, early Saturday.

"We found a car fallen in River Nakasawa last night... and found the driver's body downstream this morning," an official at Niigata police said of the drowned man.

Four other people are missing in the area, including a 93-year-old woman who was swept away in a river and a 25-year-old man who was believed to have fallen into a flooding river while driving, police said.

Officials had requested the Self-Defence Force dispatch troops to join the search for missing people and help those stranded by mudslides and floods.

A 63-year-old man was listed as missing in Fukushima, whose Pacific coasts were hit by a massive tsunami on March 11 that crippled an atomic power plant in the world's worst nuclear disaster since Chernobyl in 1986.

More than 40 people who had spent a night in cars and buses after being stranded on a road blocked by mudslides and flooding in Fukushima were rescued unhurt.

"I couldn't sleep. I had some food but couldn't swallow a bite" out of fears that further mudslides would hit the stranded cars, a woman told NHK.

The weather agency has warned quake-hit regions are more prone to mudslides as the tremors had worsened ground conditions.