The UN is warning about outbreak of diseases such as cholera following the floods. Photo: Reuters

The UN has warned that disease outbreaks could bring "a second devastating crisis" to Libya a week after a massive flash flood devastated the coastal city of Derna, sweeping thousands to their deaths.

Local officials, aid agencies and the World Health Organization "are concerned about the risk of disease outbreak, particularly from contaminated water and the lack of sanitation", the United Nations said on Monday.

Thousands of people are missing after the floods triggered by hurricane-strength Storm Daniel hit the war-scarred North African country on September 10.

Tens of thousands of traumatised residents are now homeless and badly in need of clean water, food and basic supplies amid a growing risk of cholera, diarrhoea, dehydration and malnutrition, UN agencies have warned.

Like earthquake

As rescue teams from several European and Arab countries kept up the grim search for bodies in the mud-caked wasteland of smashed buildings, crushed cars and uprooted trees, Derna survivors recounted the horror of the events.

The UN has appealed for more than $70 million to help the flood victims in Libya. Photo: Reuters

"I took nothing but my glasses and phone and fled while water was shaking the iron doors like an earthquake," the Abdel Moneim Awad al-Sheikh, 73, who was awakened in the pre-dawn hours by the sound of screams and rushing water.

He escaped with his wife by climbing up from his first floor apartment to the roof of the building with other family members.

Mohamed Abdelhafiz, a 50-year-old Lebanese man who has lived in Derna for decades, recalled that he "saw death".

"This whole area, from my house to the wadi (dry riverbed), had three or four buildings. Now, there is nothing. The ground is just mud, as though there never were any buildings here."

Unclothed bodies

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

Soldier Hamza Al-Khafifi, 45, described to AFP finding the unclothed bodies of "old, young, women, men and children" washing up on the shore a week after the disaster.

Five members of a Greek rescue team were killed in a road accident while travelling from Benghazi to Derna on Sunday, Greek officials said.

Abdeljalil said their vehicle collided with a car carrying a Libyan family, three of whose members died while two others were seriously injured.

Emergency response teams and aid have been deployed from France, Greece, Iran, Russia, Saudi Arabia, Tunisia, Türkiye and the United Arab Emirates.

Aid appeal

On Monday the UN mission in Libya said nine United Nations agencies were involved in efforts to deliver aid and support to survivors. The United Nations has launched an aid appeal for more than $71 million.

In the face of the tragedy, rival Libyan administrations appear to have set aside their differences after calls from aid groups and several countries to close ranks and collaborate in the aid effort.

On Monday the Tripoli-based government announced the launch of work to build a temporary bridge that would span the wadi that cuts through Derna.

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

TRT Afrika and agencies