Thousands of people are feared dead in Libya after Storm Daniel brought severe rain and floods to the eastern part of the country, sweeping entire neighborhoods into the sea, according to eastern Libyan officials.

Ahmed Mismari, spokesperson of the eastern based Libyan National Army (LNA), told a Monday press conference that in badly affected city of Derna alone more than 2,000 have died and between 5,000 to 6,000 people are still missing.

CNN has not been able to independently verify the number of deaths, and Mismari did not give a source for the number of dead and missing.

The Red Crescent in Benghazi earlier estimated 150 to 250 people are dead in Derna, according to Reuters

Severe pressure from the heavy rains in Derna caused dams to collapse, destroying homes and roads, say authorities.

Mismari, told a news conference that the flooding was caused by two dams collapsing in the city's south. "As a consequence, three bridges were destroyed. The flowing water carried away entire neighborhoods, eventually depositing them into the sea," he said.

The spokesman said that the "unprecedented floods occurred in the cities of Al-Bayda, Derna, Al-Marj, Tobruk, Takenis, Al-Bayada, and Battah, and all the cities and villages of Al-Jabal Al-Akhdar and the eastern coast, all the way to Benghazi."

The head of Libya's eastern parliament-backed government, Osama Hamad, described the situation as "catastrophic and unprecedented in Libya," according to a report from state news organization Libyan News Agency (LANA).

Footage shared on social media showed submerged cars, collapsed buildings and torrents of water rushing through streets.

Phone lines were down in Derna and pictures shared by the Red Crescent showed severely flooded streets.

The head of Libya's Emergency and Ambulance authority, Osama Aly, told CNN that after the dam collapse "all of the water headed to an area near Derna, which is a mountainous coastal area."

Homes in valleys that were in the line of the flood were washed away with strong muddy water currents carrying vehicles and debris, Aly said.

Aly did not confirm the number of deaths previously announced by one of Libya's governments, but said the number is not to be dismissed based on the estimates of the population in the area.

The official said they are not able to reach their own teams inside Derna after phone lines were destroyed. Other emergency teams are not able to enter the Derna due to the heavy destruction, Aly said.

Aly suggested there was negligence by authorities in preparing for the potential damage from the storm.

"The weather conditions were not studied well, the seawater levels and rainfall [were not studied], the wind speeds, there was no evacuation of families that could be in the path of the storm and in valleys," Aly said.

"Libya was not prepared for a catastrophe like that. It has not witnessed that level of catastrophe before. We are admitting there were shortcomings even though this is the first time we face that level of catastrophe," Aly told Al Hurra channel earlier.

Mediterranean storm

Hospitals in the eastern city of Bayda were evacuated after severe flooding from rainfall caused by a heavy storm, videos shared by the Medical Center of Bayda on Facebook showed.

This rain is the result of the remnants of a very strong low-pressure system, which was officially named Storm Daniel by the national meteorological services in southeastern Europe.

The storm brought catastrophic flooding to Greece last week before moving into the Mediterranean and developed into a tropical-like cyclone known as a medicane. These systems can bring dangerous conditions to the Mediterranean Sea and coastal countries, similar to tropical storms and hurricanes in the Atlantic or typhoons in the Pacific.

The remains of the storm are affecting northern Libya and will slowly head east toward northern Egypt. Rainfall for the next two days could reach 50mm -- this region averages less than 10mm across the whole of September.

"The United Nations in Libya is closely following the emergency caused by severe weather conditions in the eastern region of the country," said the United Nations Support Mission in Libya in a post on X (formerly known as Twitter).

Foreign countries have offered to send aid to the country, with Turkey's disaster agency saying Monday that it will mobilize 150 search and rescue personnel, along with tents, rescue vehicles and other supplies such as generator.

The US Embassy in Libya said on X, formally known as Twitter, that it was in "close contact with the United Nations and with authorities in Libya to determine how quickly we can bring assistance to bear where it is most needed."