For his part, Ali Abdullah Saleh, the Yemeni president, called for parliament to approve 20 billion rials ($100m) in emergency funding for rescue and rebuilding operations.

Saleh has toured some of the worst affected regions.

Mahara and Hadramaut were declared disaster zones on Friday.

Attempts to get medical supplies and relief aid to the region have been hampered as many of the roads in the area have been completely flooded.

Among the affected areas is the Unesco world heritage site of Shibam, where the area's historic mud-brick buildings are threatened with collapse.

Shibam, which was totally isolated by the flood waters, is home to more than 20,000 people and is famous for its mud-brick highrise buildings that have given the town the nickname "the Manhattan of the desert".

A cargo vessel also ran aground off the port of Nashtun in Mahra, but all 17 crew members were rescued.

Yemen is one of the poorest countries in the world and its government is already struggling to contain an uprising in the north, unrest in the south and the re-emergence of al-Qaeda in the region.

An international aid appeal has been launched.