A week after a tsunami-sized flash flood devastated the Libyan coastal city of Derna, sweeping thousands to their deaths, the international aid effort gained pace on Sunday to help the grieving survivors. 

Search-and-rescue teams wearing face masks and protective suits kept up the grim search for any survivors who may still be trapped in the mud-caked wasteland of smashed buildings, crushed cars and uprooted trees.

Traumatised residents, 30,000 of whom are now homeless in Derna alone, are in dire need of clean water, food, shelter and basic supplies amid a growing risk of cholera, diarrhoea, dehydration and malnutrition, UN agencies warn.

"In this city, every single family has been affected," said one resident, Mohammad al-Dawali.

Seir Mohammed Seir, a member of the security forces, spoke of a three-month-old girl who lived through the tragedy: "Her entire family died, she was the only one who survived."

Emergency response teams and relief goods have been deployed from France, Iran, Malta, Russia, Tunisia, Turkey and the United Arab Emirates, with more on the way from multiple other European and Arab nations.

The aid effort has been hampered by the political division of Libya, which was thrown into war and chaos after a 2011 NATO-backed uprising led to the overthrow and killing of veteran dictator Moamer Kadhafi.

The oil-rich North African country now remains split between two rival governments - a UN-backed administration in the capital Tripoli, and one based in the disaster-hit east.

Amid the chaos, the true death toll remained unknown, with untold numbers feared swept into the sea.

Thousands missing

The health minister of the eastern administration, Othman Abdeljalil, has said that 3,252 people were confirmed dead in Derna, where corpses wrapped in blankets and in body bags have lined squares and streets.

The UN Office for the Coordination of Humanitarian Affairs warned on Sunday that the eventual death toll from Derna alone could be as high as 11,300, with another 10,100 missing.

But the Libyan Red Crescent, which was cited by the UN agency, earlier denied a UN death toll of over 10,000 and called on the media to "exercise caution and accuracy".

The massive flood came as Libya was lashed on September 10 by the hurricane-strength Mediterranean Storm Daniel, which had earlier brought deadly floods to Greece, Turkey and Bulgaria.

The rapidly rising waters burst two upstream river dams in Derna, sending a late-night tidal wave crashing through the centre of the city of 100,000, sweeping entire residential blocks into the Mediterranean.

UN experts have blamed the high death toll on climatic factors as the region has sweltered under an unusually hot summer, and the legacy of Libya's war that has depleted its infrastructure, early warning systems and emergency response.

Questions are being asked about whether the disaster could not have been prevented, when cracks in the dams have been reported since 1998.

Bodies on the beach

A week on, bodies are still being found, many washing up on the sea shore of the Mediterranean, along with vast amounts of debris.

A rescue crew from Malta's Civil Protection Department said it discovered a beach strewn with bodies on Friday, the Times of Malta newspaper reported.

"There were probably 400, but it's hard to say," team leader Natalino Bezzina told the newspaper, saying access was difficult due to strong winds.

A Libyan rescue team in an inflatable boat reported seeing "perhaps 600 bodies" at sea off the Om-al-Briket region, about 20 kilometres east of Derna, according to a video shared on social networks.

The United Nations has launched an aid appeal for more than $71 million.

The aid being sent to Libya includes water, food, tents, blankets, hygiene kits, medicines and emergency surgical supplies as well as heavy machinery to help clear the debris, and more body bags.

The scale of the devastation in Derna and surrounding areas has prompted shows of solidarity across divided Libya, as volunteers in Tripoli have collected aid for the flood victims.

The International Committee of the Red Cross warned of another risk in the flood area - unexploded landmines and other ordnance left over from the war that may have been washed into areas previously free of weapon contamination.