KYUSHU (REUTERS) - Japan is sending thousands of troops to join rescue operations on the southern island of Kyushu, Prime Minister Shinzo Abe said on Saturday (July 4), after 13 people went missing in unprecedented torrential rains that threaten floods and landslides.

Images broadcast on television showed houses and cars submerged in muddy waters in the prefecture of Kumamoto, where public broadcaster NHK said the flooding Kuma River was cutting off homes and had washed away a bridge.

"The heavy rainfall is likely to continue until Sunday and people in the area are required to be on the maximum alert," Mr Abe said, adding that as many as 10,000 members of Japan's Self Defence Forces would be dispatched to the region.

More than 100 appeals for rescue to local authorities could not be immediately responded to, NHK said.

However, Japan's Meteorological Agency downgraded its alert from the highest level it had initially posted to warn against floods and landslides triggered by the rain "never seen" before in the region, the broadcaster added.