About a dozen women hunch over sewing machines in Libya's capital, urgently making clothes for the living, and shrouds for the dead, two weeks after a huge flood devastated the eastern city of Derna.

In the war-battered north African country that has long been divided between two rival governments, the tragedy that killed thousands has sparked a nationwide sense of solidarity.

"Our centre was already helping needy families, so you can imagine our mobilisation when it involves a disaster of this magnitude," said Mohamed Kamour, the director of the centre that trains women to become dressmakers.

Since the flood struck on September 10, the apprentices have worked at full speed, cutting and sewing fabric for the needy in Derna, a city more than 1,300 kilometres (800 miles) to the east.

All normal courses have been suspended for the aid effort, said Kamour, whose workshop usually helps widows and divorced women gain financial independence.

"That is the priority," he said. "We interrupted all types of training."

The workshop has already sent 1,300 school uniforms, 850 abayas and 650 shrouds to cover corpses to Derna, and a second shipment is being prepared.

Derna had a population of about 100,000 before the flash flood broke through two ageing dams after a hurricane-strength storm lashed the area.

The official death toll passed 3,800 on Saturday.

The flood, which witnesses likened to a tsunami, may have left 10,000 or more people missing, international aid groups said.

Many were swept out to sea, from where bodies are still washing ashore. Others are thought to be buried beneath the mud and debris that carpets entire neighbourhoods of Derna.

- Libya 'unites us' -

Since a 2011 NATO-backed revolt toppled longtime dictator Moamer Kadhafi, Libya has seen more than a decade of stop-start conflict.

It is now divided between an internationally-recognised administration in Tripoli in the west and another in the east, whose forces launched a failed assault on the capital which ended in a 2020 ceasefire.

Despite Libya's political split, Kamour said he received the requests of stricken residents from charities based in the east, and has stepped up production in response.

The women stand over a large table crowded with the day's output, which they sort and fold: grey and green abayas, a traditional full-length robe; white medical smocks; shrouds for the bodies.

Karima Wanis, 39, the centre's trainer, said she feels as if she lost members of her own family.

While sewing machines hummed in the background, she said that it is "normal to come to the aid of our Derna brothers".

"We are part of the same family" Wanis said. "West or East. Ultimately, it's Libya that unites us."

- Volunteer effort -

Yann Fridez, head of the Libya delegation of the International Committee of the Red Cross, spent three days in the disaster zone where he reported seeing people from all regions of Libya, even the southern city of Sebha hundreds of kilometres away.

People went to Derna "on their own initiative, tribes did too," Fridez said about the country where tribal structures and loyalties remain important.

Restaurateurs have organised meals to feed the displaced.

Business people and others with the means have also mobilised in the country's west and the south to help those suffering.

The International Organization for Migration said on Thursday that more than 43,000 people have been uprooted from the disaster zone.

Appeals to shelter them have spread on social media.

"A family has just arrived in Tripoli from Derna. They quickly need lodging," one Facebook post said. In response, volunteers offered their telephone numbers, a first step in providing help.

Libyan authorities said it is difficult for them to respond to survivors' urgent needs, but international assistance has arrived from several countries and humanitarian groups.

Qatar's embassy in Libya announced the arrival on Saturday in Benghazi of two planes carrying 60 tonnes of assistance. That brings to eight the number of shipments sent by the Gulf emirate.

On Thursday a plane bringing aid from the United States also landed in Benghazi, the eastern city about 300 kilometres by road from Derna.