Rivers burst their banks in Japan, forcing millions from their homes with more rain expected in some areas.

Nearly 80 people are believed to be dead in Japan after three days of torrential rain made rivers burst their banks.

The government put the number of victims at 48 with 28 others presumed dead as it issued new disaster warnings on Kyushu and Shikoku islands on Sunday.

The torrential downpours have caused flash flooding and landslides across central and western parts of the country, prompting evacuation orders for more than two million people.

“Rescues, saving lives and evacuations are a race against time,” Prime Minister Shinzo Abe said as he met a government crisis cell set up to respond to the disaster.

“There are still many people whose safety has yet to be confirmed,” he added.

The assessment of the number of injuries and deaths has been difficult because of the wide area affected by the rainfall, flooding and landslides.

The torrential downpours have caused flash flooding and landslides [Kyodo via Reuters]

Emergency warnings for severe rain remained in effect for three prefectures, with 300mm predicted to fall by Monday morning in parts of the smallest main island of Shikoku.

Drier weather is expected, however, in much of the country over the next few days as the band of rain responsible for the floods and landslides weaken while it drifts into the northwest Pacific.

Authorities warned landslides could strike even after the rain subsides as the calamity shaped up to potentially be the worst in decades.

Landslide warnings were issued in more than a quarter of the nation’s prefectures.

Landslide warnings were issued in more than a quarter of the nation’s prefectures [Kyodo via Reuters]

Rescues by helicopter

As the rain fell, some people fled to rooftops and balconies and waved at hovering rescue helicopters. Military paddle boats were also being used to take people to dry land.

The Japan Meteorological Agency said three hours of rainfall in one area in Kochi prefecture reached an accumulated 263mm, the highest since such records started in 1976.

Throughout the hard-hit areas, rivers swelled and parked cars sat in pools of water. Japan has sent troops, firefighters, police and other disaster relief. People have also taken to social media to plead for help.