The death toll from floods in the eastern Libyan city of Derna has risen above 2,000, local media reported.
Further thousands are believed to be missing, Libyan News Agency (LANA) cited Ossama Hamad, head of Libya's eastern parliament-backed government, as saying on Monday.
Hamad also said entire residential blocks were erased after they were swept away by the floods in Derna.
Early on Monday, the head of Libya’s Tripoli-based unity government, Abdul Hamid Dbeibeh, declared all areas exposed to the storm and floods as "disaster zones."
Dbeibeh also announced three days of national mourning for the victims of deadly floods that ravaged the North African country.
Storm Daniel swept several areas in eastern Libya on Sunday, most notably the cities of Benghazi, Bayda, and Al Marj, as well as Soussa and Derna, according to an Anadolu reporter in the field.
The destruction appears greatest in Derna, the city where the chaos left it with inadequate infrastructure. Libya remains divided between two rival administrations, one in the east and one in the west, Libya's internationally-recognised Government of National Accord (GNA)
Video by residents of the city posted online showed major devastation. Entire residential areas were erased along a river that runs down from the mountains through the city centre. Multi-storey apartment buildings that once stood well back from the river were partially collapsed into the mud.
'A disaster zone'
In Derna, local media said the situation was catastrophic with no electricity or communications.
Essam Abu Zeriba, the interior minister of the east Libya government, said more than 5,000 people were expected to be missing in Derna. He said many of the victims were swept away towards the Mediterranean.
"The situation is tragic," he declared in a telephone interview on the Saudi-owned satellite news channel Al Arabiya. He urged local and international agencies to rush to help the city.
Hamad declared Derna a disaster zone after heavy rainfall and floods destroyed much of the city, which is located in the delta of the small Wadi Derna on Libya's east coast.
The Libyan government declared a state of emergency on Saturday and suspended classes as a precaution ahead of the storm, which made landfall overnight.
Storm Daniel is expected to arrive in parts of west Egypt on Monday, and the country’s meteorological authorities warned about possible rain and bad weather.