TOKYO: At least six people died, 18 were missing and 50,000 ordered to evacuate as the heaviest rainfall on record pounded the southwestern Japanese island of Kyushu, officials and reports said Thursday.

Emergency workers in Kumamoto prefecture responded to multiple reports of mudslides swallowing houses and people being trapped, with access roads blocked by mud or gushing water, officials said.

Troops have been deployed with nearly 100 millimeters (four inches) of rain falling in a hour in some parts of the area.

"Particularly in Kumamoto and Oita prefectures, we are seeing the heaviest rain that (the region) has ever experienced," the Japan Meteorological Agency said.

Kumamoto prefecture confirmed the deaths of four women in their 60s, 70s and 80s, after waters destroyed their houses, while media reported that a man had also died there.

The local government has received reports of at least 17 missing people, many of them swept away by swollen rivers or missing after their homes were destroyed.

"We are receiving many requests for rescuers and reports of mudslides. We are responding to the calls as swiftly as we possibly can," a Kumamoto disaster official said.

"We may get more rain later, and we are increasing our alert level for rivers overflowing," another official said.

In neighboring Oita prefecture, a man in his 70s died after being swept into a raging river, while another man remained missing.

Prime Minister Yoshihiko Noda promised full relief efforts to help affected residents.

"I have heard that this is a record for heavy rainfall. We will take effective measures," he said in a legislative session.

Self Defense Force troops have been deployed to the region for disaster relief efforts at the request of local governors.

The prime minister's office in Tokyo has established a liaison office to coordinate efforts among central government ministries to deal with the disaster.

In Kumamoto prefecture more than 17,000 households had been ordered to evacuate, with 5,000 more advised to seek shelter elsewhere.

Oita authorities issued evacuation orders to nearly 15,000 people and advised a further 10,000 to leave.

In all, more than 50,000 people in Oita and Kumamoto received evacuation orders, according to local media.