The United Nations has said most of the deaths in flash floods that tore through Libya could have been “avoided,” as relief workers struggle to deliver crucial aid in a humanitarian effort stifled by political divisions and debris from the disaster.

At least 5,300 people have died in Libya and thousands more are feared missing after entire buildings were “wiped out” when a seven-meter wave hit the northern coastal city of Derna, the International Committee of the Red Cross (ICRC) said on Thursday.

The unprecedented rainfall engulfed cities in the North African nation last week, rupturing two dams in the country’s northeast and sending a deluge of water to Derna, which has seen the worst of the devastation.

“If there would have been a normally operating meteorological service, they would have issued the warnings and also the emergency management of this would have been able to carry out evacuations of the people and we would have avoided most of the human casualties,” Petteri Taalas, the UN’s World Meteorological Organization (WMO) secretary-general, told reporters in a news conference in Geneva on Thursday.

“Of course, we cannot fully avoid economic losses but we could’ve also minimized those losses by having proper services in place,” Talaas added.

Talaas said the WMO has tried to interact with Libyan officials on improving these mechanisms, but because the “security situation in the country is so difficult, it is difficult to go there.”

Libya has been riven by political turmoil since civil war erupted in 2014, and now has two rival governments. Each is reporting conflicting numbers for victims following the catastrophic floods in the country.

While the eastern parliament-backed government reported at least 5,300 people dead, the internationally recognized government in Tripoli reports more than 6,000 people have died. CNN is unable to independently verify the number of deaths or those missing.

‘Single wave tsunami’

The head of the ICRC’s Libya delegation said it will take “many months, maybe years,” for residents in Derna to recover from the scale of damage, after a seven-meter wave thrashed the northern coastal city this week.

“This disaster was violent and brutal. A wave 7 metres high wiped-out buildings and washed infrastructure into the sea. Now family members are missing, dead bodies are washing back up on shore, and homes are destroyed,” Yann Fridez said.

“It will take many months, maybe years, for residents to recover from this huge level of damage.”

The ICRC had a team in Derna to support families with micro-economic activities when the floodwaters overwhelmed the city, adding it will distribute 6,000 body bags to forensic teams in the eastern city of Benghazi to “ensure dignified treatment of the dead.”

Access to the flood-hit areas remains a “major challenge” because roads were destroyed, the ICRC said.

Libya’s former minister Health Minister Reida El Oakley told CNN’s Becky Anderson on Wednesday that “a huge wave, as high as a six-story building or higher, swept the whole country as a single wave tsunami.”

Khaled Al-Shuwaihed, a Libyan citizen, said the situation in Derna “was a catastrophe.”

“It was a catastrophe, all of my friends are dead,” al-Shuwaihed told Reuters on Thursday.

“One of my friends at the very beginning was filming from the top of the valley, my friend, he was filming, he died. Someone named Nasir Fatoury and his children (are said to be dead) but these are all rumors at this point, nothing has been confirmed. One of my friends and his five children, only one of them found us.”

Aid slowly arrives

Medical volunteers said they were overwhelmed by the scale of human disaster in Derna, as aid slowly began to arrive on Thursday amid fears of waterborne diseases.

More than 30,000 people have been displaced in Derna, the UN’s International Organization for Migration (IOM) said on Wednesday. Meanwhile bodies piled up near defunct health facilities, despite the need to treat survivors of the disaster.

Khaled Hamid, the general manager at a Libyan NGO, said aid donations were inadequate for the number of people needing treatment.

“The first step was easy, we collected money from equipments and donations from inside and outside the organization. We didn’t expect that people would sympathize with us to this extent, and thank God we received very good support,” Hamid told Reuters.

“This is a drop in the ocean of the needs we need for Derna, but we saw while coming here that people are coming here from different cities of Libya, from Misrata, Tripoli, Zawiya, from every city.”

On Thursday, the marine port into Derna became accessible for ships with a minimum draft level of 6.5 meters to deliver humanitarian aid to the badly damaged area, the Libyan Ports and Maritime Transport Authority said.

A committee has been established to improve operations at the port, the statement said, adding that the primary objective is to expedite the aid delivery to the region.

The Ministry of Transport is led by the internationally recognized government in, Tripoli, in west Libya, led by Dbeibeh.

International leaders from countries including Tunisia, Turkey, Algeria and Italy pledged donations, but questions remain over how aid will reach parts of Libya controlled by rival forces.

Saudi Arabia said it would send food and shelter through the Saudi aid agency KS Relief in coordination with the Libyan Red Crescent and other aid groups.

The European Union pledged medical personnel and equipment, rescue boats, helicopters and other vital aid, after releasing $537,000 in humanitarian funding. (CNN)

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