The US military joined relief efforts on Monday in southern Japan for areas devastated by two powerful earthquakes as local rescuers combed through debris looking for 10 people still reported missing.

Authorities said at least 42 people had died and nearly 1,100 were injured in the two quakes that hit the region near Kumamoto city late on Thursday and early on Sunday.

Rescuers were redoubling search efforts on the southern island of Kyushu, where many areas were cut off by landslides and road and bridge damage. Forecasts for heavy rains, which would make land and collapsed buildings even more unstable, added to the urgency.