The destruction appeared greatest in Derna, a city formerly held by Islamic extremists in the chaos that has gripped Libya for more than a decade and left it with crumbling and inadequate infrastructure. Libya remains divided between two rival administrations, one in the east and one in the west, each backed by militias and foreign governments.

The confirmed death toll from the weekend flooding stood at 61 as of late Monday, according to health authorities. But the tally did not include Derna, which had become inaccessible, and many of the thousands missing were believed carried away by waters.

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-story apartment buildings that once stood well back from the river were partially collapsed into the mud.

In a phone interview with al-Masar television station Monday, Prime Minister Ossama Hamad of the east Libyan government said 2,000 were feared dead in Derna and thousands were believed missing. He said Derna has been declared a disaster zone.

Ahmed al-Mosmari, a spokesman for the country’s armed forces based in the east, told a news conference that the death toll in Derna had surpassed 2,000. He said there were between 5,000 and 6,000 reported missing. Al-Mosmari attributed the catastrophe to the collapse of two nearby dams, causing a lethal flash flood.

Since a 2011 uprising that toppled and later killed long-time ruler Moammar Gadhafi, Libya has lacked a central government and the resulting lawlessness has meant dwindling investment in the country’s roads and public services and also minimal regulation of private building. The country is now split between rival governments in the east and west, each backed by an array of militias.

Derna itself, along with the city of Sirte, was controlled by extremist groups for years, at one point by those who pledged allegiance to the Islamic State group, until forces loyal to the east-based government expelled them in 2018.

At least 46 people were reported dead in the eastern town of Bayda, Abdel-Rahim Mazek, head of the town’s main medical centre said. Another seven people were reported dead in the coastal town of Susa in northeastern Libya, according to the Ambulance and Emergency Authority. Seven others were reported dead in the towns of Shahatt and Omar al-Mokhtar, said Ossama Abduljaleel, health minister. One person was reported dead Sunday in the town of Marj.

The Libyan Red Crescent said three of its workers had died while helping families in Derna. Earlier, the group said it lost contact with one of its workers as he attempted to help a stuck family in Bayda. Dozens of others were reported missing, and authorities fear they could have died in the floods that destroyed homes and other properties in several towns in eastern Libya, according to local media.

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.

In a post on X, the US Embassy in Libya said it was in contact with both the UN and Libyan authorities and was determining how to deliver aid to the most affected areas.

Over the weekend, Libyans shared footage on social media showing flooded houses and roads in many areas across eastern Libya. They pleaded for help as floods besieged people inside their homes and in their vehicles.

Ossama Hamad, the prime minister of the east Libya government, 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 prime minister also announced three days of mourning and ordered flags across the country to be lowered to half-staff.

Controlling eastern and western Libya, Cmdr. Khalifa Hifter deployed troops to help residents in Benghazi and other eastern towns. Ahmed al-Mosmari, a spokesperson for Hifter’s forces, said they lost contact with five troops who were helping besieged families in Bayda.

Foreign governments sent messages of support on Monday evening. Sheikh Mohammed bin Zayed Al Nahyan, the president of the United Arab Emirates, said his country would send humanitarian assistance and search-and-rescue teams to eastern Libya, according to the UAE’s state-run WAM news agency.

Turkey, which supports the country’s Tripoli-based government in the west, also expressed condolences, along with neighbouring Algeria.

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.