The death toll from floods in Libya in one city alone stands at more than 1,000, a senior official who visited the eastern port of Derna has said.

"Bodies are lying everywhere," the minister from the eastern-based government told Reuters news agency.

Much of Derna, which has about 100,000 residents, is under water after two dams and four bridges collapsed.

The flooding, which has also devastated other coastal areas, is as a result of a Storm Daniel which hit on Sunday.

"The number of bodies recovered in Derna is more [than] 1,000," Hichem Chkiouat, the aviation minister and part of the eastern government's emergency response committee, told Reuters by phone.

He said the final death toll was expected to be much higher.

"I am not exaggerating when I say that 25% of the city has disappeared. Many, many buildings have collapsed."

The eastern cities of Benghazi, Soussa and Al-Marj have also all been affected.

Earlier, Eastern Prime Minister Osama Hamad told a Libyan TV channel it was estimated that 2,000 people had died and thousands were missing: "Entire neighbourhoods in Derna have disappeared, along with their residents... swept away by water."

Alongside areas in the east, the western city of Misrata was among those hit by the floods.

Libya has been in political chaos since long-serving ruler Col Muammar Gaddafi was overthrown and killed in 2011 - leaving the country effectively split with an interim, internationally recognised government operating from the capital, Tripoli, and another one in the east.

According to Libyan journalist Abdulkader Assad, this is hampering rescue efforts as the various authorities are not able to respond with agility to a natural disaster.

"There are no rescue teams, there are no trained rescuers in Libya. Everything over the last 12 years was about war," he told the BBC.

"There are two governments in Libya... and that is actually slowing down the help that is coming to Libya because it's a little bit confusing. You have people who are pledging help but the help is not coming."