Up to 10,000 people are reported missing after Storm Daniel struck on Sunday, according to the Red Crescent.
Storm Daniel caused devastating flooding across the North African country, including its major cities of Benghazi and Derna.
The coastal city of Derna was badly hit with authorities fearing up to 1,000 dead. A government spokesman said nearly a quarter of the city was totally destroyed.
United Nations relief chief Martin Griffiths has voiced deep concern over the flood disaster in Libya.