About 100,000 people north of Tokyo were forced to leave their homes on Thursday after the Kinguawa River surged over its banks and flooded nearby towns. Helicopters rescued residents from rooftops after a wall of water hit the town of Joso, 50 kilometers (30 miles) northeast of the capital Tokyo.

"The prefecture has requested assistance from the Self-Defence Forces and police helicopters from the region. We are receiving their help," a official from the Ibaraki prefecture - where Joso is located - reported to news agency AFP. "We do not have updated information about the damage, but we know it is extensive and affected wide areas," he added.

Japanese officials also advised an additional 800,000 people to evacuate their homes in the eastern part of the country.

"The government will work as one to prioritize the safety of the people and do our best to prevent any further disaster," Prime Minister Shinzo Abe told reporters.

Dramatic rescue

A 63-year-old woman went missing after a landslide hit her home, while a Joso resident in his 70s disappeared when flood waters carried away his home. Rescue officials said they had been struggling to keep up with the calls for help.

Aerial footage from national broadcaster NHK showed dramatic images of rescue workers grabbing people one-by-one from rooftops, while another man clung to a utility pole nearby. In another image, an elderly couple sat on a rooftop holding onto two dogs while awaiting rescue.

The unprecedented rainfall followed on the heels of tropical storm Etau, which blew through the central part of the country on Wednesday. Joso and the surrounding area reported rainfall of 600 mm (24 inches) so far with weather officials anticipating at least 200 mm (8 inches) more by the end of the week.

rs/se (AP, AFP, dpa, Reuters)