Libya was reeling Wednesday from a massive flood disaster that killed at least 2,300 people when a surge of water devastated the eastern city of Derna, leaving another 10,000 missing according to the Red Cross.

Relief missions gathered pace with Turkey, Egypt and the United Arab Emirates among the first nations to rush aid to the war-scarred country, and the UN pledging $10 million in support for survivors, including 30,000 people left homeless.

The Mediterranean coastal city of Derna was hit by a huge flash flood late Sunday that witnesses likened to a tsunami after two upstream dams burst amid torrential rains brought by Storm Daniel.

The wall of water swept away entire buildings, vehicles and the people inside them. Many were swept out into the Mediterranean, with bodies washing up on beaches littered with debris and car wrecks.

Traumatised survivors have dug through the mud-caked ruins of shattered buildings to recover victims' bodies, many of which have been buried in mass graves.

The confirmed death toll in the politically fractured country reached 2,300 by Tuesday afternoon, but some regional officials were quoted as giving figures more than twice as high.

'Another 10,000 people were still missing," said Tamer Ramadan of the International Federation of Red Cross and Red Crescent Societies.

"The death toll is huge and might reach thousands," Ramadan said Tuesday, adding that the organisation had independent sources saying that "the number of missing people is hitting 10,000 persons so far".

Oil-rich Libya is still recovering from the years of war and chaos that followed the Nato-backed uprising which toppled and killed longtime dictator Muammar Gaddafi in 2011.

The country has been left divided between two rival governments -- the UN-brokered, internationally recognised administration based in Tripoli, and a separate administration in the disaster-hit east.

Media reports quoted an Interior Ministry spokesman of the eastern-based government as saying "more than 5,200" people had died in Derna.

The city, a 300-kilometre (190 mile) drive east of Benghazi, is ringed by hills and bisected by a riverbed that is usually dry in summer, but which became a raging torrent that also destroyed several bridges.

"Mudslides and flooding also hit nearby areas of eastern Libya where entire villages have been overwhelmed by the floods and the death toll continues to rise," aid group the Norwegian Refugee Council said.

"Communities across Libya have endured years of conflict, poverty and displacement. The latest disaster will exacerbate the situation for these people. Hospitals and shelters will be overstretched."

With global concern spreading, several nations offered urgent aid and rescue teams to help address what one UN official called "a calamity of epic proportions".

"The United Nations allocated $10 million for disaster relief," said Martin Griffiths, Under-Secretary-General for Humanitarian Affairs and Emergency Relief Coordinator.

"Storm Daniel has claimed thousands of lives, caused widespread damage and wiped out livelihoods in eastern Libya," he wrote on X, formerly Twitter, adding: "We stand with the people of Libya at this difficult time."

Authorities said rescue teams from Turkey have arrived in eastern Libya, and Algeria, France, Italy, Qatar and Tunisia also pledged to help.

The United Arab Emirates sent two aid planes carrying 150 tonnes of food, relief and medical supplies to Benghazi, and France said it was sending a field hospital and around 50 military and civilian personnel.

A Kuwaiti flight took off Wednesday with 40 tonnes of supplies, and Jordan sent a military plane loaded with food parcels, tents, blankets and mattresses.

Climate experts have linked Libya's deadly disaster to a combination of the impacts of a heating planet and of the country's years of political chaos and underinvestment in infrastructure.

Hurricane-strength Mediterranean storms such as Daniel -- which earlier hit Turkey, Bulgaria and Greece -- are known as "medicanes" which can gain strength as warmer air absorbs more moisture.

Climate-linked extreme weather events tend to be the deadliest in strife-torn and poor countries that lack good infrastructure, early warning systems and emergency response services.

"As the world heats up, Libya's disaster is illustrative of the type of devastating flooding event we may expect increasingly in the future," said Bristol University climate science professor Lizzie Kendon.