At least 48 people have been killed or are missing in Yemen, following torrential rains.
Most of the casualties are in the eastern province of Hadhramawt, hit by a tropical storm earlier this week.
An air rescue operation is under way. Damage is extensive because most homes in the area are made of mud brick.
Reports say the floodwaters are threatening the historic high-rise mud buildings of Shibam - a Unesco world heritage site.
A reporter for the Associated Press news agency in Shibam said he had watched a two-storey mud-brick house disintegrate on Saturday.
There has also been severe flooding in the capital, Sanaa, in recent days.
On Saturday at least six aircraft took off from Sanaa carrying tents, food and medicine to Hadramawt province, airport officials told AFP news agency.
Severe flash floods struck Yemen in 2006, leaving several dead and sweeping away buildings.
PHOTO CAPTION
Map of Yemen
BBC