DERNA, Libya, Sept 12 (Reuters) - Thousands of people were killed and at least 10,000 were missing in Libya in floods caused by a huge Mediterranean storm that burst dams, swept away buildings, and wiped out as much as a quarter of the eastern coastal city of Derna.

A senior medic in Derna told Reuters that more than 2,000 people were dead, while eastern Libya officials cited by local television were estimating a toll above 5,000.

Storm Daniel barrelled across the Mediterranean into a country divided and crumbling after more than a decade of conflict.

In Derna, a city of around 125,000 inhabitants, Reuters journalists saw wrecked neighborhoods, their buildings washed out and cars flipped on their roofs in streets covered in mud and rubble left by a wide torrent after dams burst.

Mohamad al-Qabisi, director of the Wahda Hospital, said 1,700 people had died in one of the city's two districts and 500 had died in the other.

Reuters journalists saw many bodies laid out on the ground in the hospital corridors. As more bodies were brought to the hospital people looked at them, trying to identify missing family members.

"Bodies are lying everywhere - in the sea, in the valleys, under the buildings," Hichem Abu Chkiouat, minister of civil aviation in the administration that controls the east, told Reuters by phone shortly after visiting Derna.

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

The local al-Masar television said the eastern administration's interior minister had said more than 5,000 people died.

Other eastern cities, including Libya's second-biggest city Benghazi, were also hit by the storm. Tamer Ramadan, head of a delegation of the International Federation of the Red Cross and Red Crescent Societies, said the death toll would be "huge".

"We can confirm from our independent sources of information that the number of missing people is hitting 10,000 so far," he told reporters via video link.

The United Nations Office for the Coordination of Humanitarian Affairs said emergency response teams had been mobilised to help on the ground

As Turkey and other countries rushed aid to Libya, including search and rescue vehicles, rescue boats, generators, and food, distraught Derna citizens rushed home in search of loved ones.

'NEVER FELT AS FRIGHTENED'

In Derna, Mostafa Salem, 39, said he had lost 30 of his relatives. "Most people were sleeping. Nobody was ready," Salem told Reuters.

Raja Sassi, 39, survived the flood with his wife and small daughter after the water had reached an upper floor, but the rest of his family had died, he said.

"At first we just thought it was heavy rain but at midnight we heard a huge explosion and it was the dam bursting," he said.

At Tripoli airport in northwest Libya, a woman wailed as she received a call saying most of her family were dead or missing. Her brother-in-law, Walid Abdulati, said: "We are not speaking about one or two people dead, but up to 10 members of each family dead."

Karim al-Obaidi, a passenger on a plane from Tripoli to the east, said: "I have never felt as frightened as I do now ... I lost contact with all my family, friends, and neighbors."

An interior ministry spokesperson told Al Jazeera that naval teams were searching for the "many families that were swept into the sea in the city of Derna".

FLOOD WARNING

Derna is bisected by a seasonal river that flows from the highlands to the south and is normally protected from flooding by dams.

A video posted on social media showed remnants of a collapsed dam 11.5 km (7 miles) upstream of the city where two river valleys converged, now surrounded by huge pools of mud-colored water.

"There used to be a dam," a voice can be heard saying in the video. Reuters confirmed the location based on the images.

In a research paper published last year, hydrologist Abdelwanees A. R. Ashoor of Libya's Omar Al-Mukhtar University said repeated flooding of the seasonal riverbed, or wadi, was a threat to Derna. He cited five floods since 1942 and called for immediate steps to ensure regular maintenance of the dams.

"If a huge flood happens the result will be catastrophic for the people of the wadi and the city," the paper said.

Pope Francis was among world leaders who said they were deeply saddened by the deaths and destruction in Libya. U.S. President Joe Biden sent his condolences and said Washington was sending emergency funds to relief organizations.

Libya is politically split between east and west and public services have fallen apart since a 2011 NATO-backed uprising that prompted years of factional conflict.

The internationally recognized government in Tripoli does not control eastern areas but has dispatched aid to Derna, with at least one relief flight leaving from the western city of Misrata on Tuesday, a Reuters journalist on the plane said.