Several people reported missing after powerful rains lash southern Japan

Several people have been either injured or reported missing after heavy rains on Japan's southern island of Kyushu caused flooding, mudslides and travel chaos on Monday.

Authorities said evacuation orders were issued to tens of thousands in Kumamoto and six other prefectures in the region. Troops were deployed to provide fresh water to residents in affected areas.

Rescue workers searched for those missing, including a man who vanished while three of this family members waited in a car to head to an evacuation centre as a mudslide hit.

In Kumamoto, an elderly woman was found inside a vehicle that fell into a river. Three others were reported missing after falling into bursting rivers.

An additional two people were also reported missing in the nearby Fukuoka prefecture.

Local television footage showed residents wading through knee-deep floodwater as muddy water gushed down, carrying broken trees and branches.

Japanese Prime Minister Shigeru Ishiba said he had initiated search and rescue operations for those missing.

Residents should use "maximum caution," he urged. He added citizens should "prioritise actions to save your lives."

The rains caused chaos over Japan's Buddhist "Bon" holiday week. Bullet trains and local train services were suspended between Kagoshima and Hakata in northern Kyushu.

The country's Meteorological Agency said on Monday it had issued the highest-level warning in the Kumamoto prefecture, saying rainfall exceeded 40 centimetres in the last twenty four hours. More was expected throughout Tuesday afternoon, it added.

The agency later downgraded its alert for Kumamoto as showers moved east toward the Tokyo region, but kept a lower-level warning for western Japan, which is set to expect up to 20 centimetres of rainfall by noon on Tuesday.