Aid groups have warned of growing risk posed by the spread of disease that could compound the humanitarian crisis in Libya, as hopes of finding more survivors fade days after deadly flooding.

Sunday's flood submerged the port city of Derna, washing thousands of people and homes out to sea after two upstream dams burst under the pressure of torrential rains triggered by the hurricane-strength storm.

Conflicting death tolls have been reported, with officials in the east of the divided country giving different estimates, and one speaking of at least 3,840 dead.

Aid organisations like Islamic Relief and Doctors Without Borders (MSF) have warned that the upcoming period could see the spread of disease as well as grave difficulties in delivering aid to those most in need.

Islamic Relief warned of a "second humanitarian crisis" after the flood, pointing to the "growing risk of water-borne diseases and shortages of food, shelter and medicine".

"Thousands of people don't have anywhere to sleep and don't have food," said Salah Aboulgasem, the organisation's deputy director of partner development.

"In conditions like this, diseases can quickly spread as water systems are contaminated," he added. "The city smells like death. Almost everyone has lost someone they know."

MSF meanwhile said it was deploying teams to the east to assess water and sanitation.

"With this type of event we can really worry about water-related disease," said Manoelle Carton, MSF's medical coordinator in Derna, who described efforts to coordinate aid as "chaotic".

But the Red Cross and the World Health Organization pointed out that contrary to widespread belief, the bodies of victims of natural disasters rarely pose a health threat.

- Appeals for aid -

 

An AFP journalist in Derna said central neighbourhoods on either side of the river, which normally dries up at this time of year, looked as if a steam roller had passed through, uprooting trees and buildings and hurling vehicles onto the port's breakwaters.

Stephanie Williams, a US diplomat and former UN envoy to Libya, urged global mobilisation to coordinate aid efforts in the wake of the flood in a social media post.

She warned of the "predilection of Libya's predatory ruling class to use the pretext of 'sovereignty' and 'national ownership' to steer such a process on their own and in a self-interested manner".

In a Friday night news conference, Ahmed al-Mesmari, the spokesman for east-based military strongman Khalifa Haftar pointed to "enormous needs for reconstruction".

The United Nations launched an appeal for more than $71 million to assist hundreds of thousands in need and warned the "extent of the problem" remains unclear.

"We don't know the extent of the problem," UN aid chief Martin Griffiths said Friday in Geneva, as he called for coordination between Libya's two rival administrations -- the UN-backed, internationally recognised government in Tripoli, and one based in the disaster-hit east.

Teams from the Libyan Red Crescent are "still searching for possible survivors and clearing bodies from the rubble in the most damaged areas" of Derna, its spokesman Tawfik Shoukri told AFP.

Other teams were trying to deliver much-needed aid to families in the eastern part of the city, which had been spared the worst of the flooding but was cut off by road, he added.

He pointed to the "very high" level of destruction in the city, but refused to give figures for the number of victims.

While most fear the death toll will be much higher, Tamer Ramadan of the International Federation of Red Cross and Red Crescent Societies said there was still hope of finding survivors but also declined to give a figure.

The International Organization for Migration meanwhile said "over 38,640" people had been left homeless in eastern Libya, 30,000 of them in Derna alone.