Residents of the devastated Libyan city of Derna desperately searched for missing relatives as rescue workers appealed for more body bags, after a catastrophic flood that killed thousands of people and swept many out to sea.

Swathes of the Mediterranean city were obliterated by a torrent of water unleashed by a powerful storm that swept down a usually dry riverbed on Sunday night, bursting dams above the city. Multistorey buildings collapsed with sleeping families inside.

Spokesperson of the interior ministry Lieutenant Tarek al-Kharraz on Wednesday told the AFP news agency that 3,840 deaths had been recorded in the Mediterranean city so far, including 3,190 who have already been buried. Among them were at least 400 foreigners, mostly from Sudan and Egypt.

Meanwhile, Hichem Abu Chkiouat, minister of civil aviation in the administration that runs eastern Libya, told the Reuters news agency more than 5,300 dead had been counted so far, and said the number was likely to increase significantly and might even double.

Derna Mayor Abdulmenam al-Ghaithi told Saudi-owned Al Arabiya television the estimated number of deaths in the city could reach between 18,000 to 20,000 based on the number of districts destroyed by the flood.