More than 5,300 people are believed to have died after floods in the Libyan city of Derna, a local minister said.
“The sea is constantly dumping dozens of bodies,” said Hisham Chkiouat, from Libya’s eastern administration.
There have been calls for more humanitarian support as victims lie wrapped in body bags and others have been buried in mass graves.
A tsunami-like river of floodwater swept through Derna on Sunday after a dam burst during Storm Daniel.
Rescue teams are digging through the rubble of collapsed buildings in the hope of finding survivors.
Officials say at least 10,000 people are feared missing or dead.
Libyan doctor Najib Tarhoni, who has been working in a hospital near Derna, said more support is needed.
“I have friends in the hospital here who have lost most of their families … they’ve lost everyone,” he told BBC Radio 4’s World at One.
“We just need people who understand the situation – logistic help, dogs that can actually smell people and get them from under the ground. We just need the humanitarian help, people who actually know what they are doing.”
The head of the Libyan doctors’ union Mohammed al-Ghoush told Turkish media there was an urgent need for specialised forensic and rescue teams and others specialised in recovering bodies.
Médecins Sans Frontières (MSF) said an emergency team will arrive in Derna on Thursday “to assess medical needs and donate emergency medical kits to care for the wounded and body bags to the Libyan Red Crescent”.
Watch: Libya doctor calls for urgent flood rescue help
Streets are covered in mud and rubble, and are littered with upturned vehicles.
Mr Chkiouat, a local official, said some areas of Derna have “vanished, completely disappeared”.
“So imagine a residential area has been destroyed completely, you cannot see it, it’s not existing anymore.
“I’ve never seen anything like this before. It’s by all means a tsunami.”
Johr Ali, a Libyan journalist currently in Istanbul whose family is in the country, said it was like “doomsday”.
“The screams of the kids, the dead bodies around the streets,” he told BBC Radio 4’s Today programme.
He explained he spoke to a family who were the only ones to have survived the floods in their neighbourhood.
“They described the situation when the floods went away, saying a woman was hanging in the street lights because she was taken away by the flood.
“She stayed there and died there. They eye-witnessed that, they eye-witnessed their nephew dead in the streets, thrown away by water.”
People say the amount of water is indescribable, he said.
“Tens of thousands are either dead or beneath the soil. The water took the ground beneath them and threw them into the sea.”
The floods have claimed the lives of a number of elite footballers, according to the Libya Football Federation.
The LFF has officially announced the deaths of four footballers in the region: Shaheen Al-Jamil, Monder Sadaqa and brothers Saleh Sasi and Ayoub Sasi.
The United Nations has called the deadly floods a “calamity of epic proportions”.
The cities of Soussa, Al-Marj and Misrata were also affected by Sunday’s storm.
Libya has been in political chaos since long-serving ruler Col Muammar Gaddafi was overthrown and killed in 2011 – leaving the oil-rich nation effectively split with an interim, internationally recognised government operating from the capital, Tripoli, and another one in the east.
But despite the split, the government in Tripoli has sent medical supplies, body bags, doctors and paramedics.
Derna, about 250km (155 miles) east of Benghazi along the coast, is surrounded by the nearby hills of the fertile Jabal Akhdar region.
The city was once where militants from the Islamic State group built a presence in Libya, after Gaddafi’s fall. They were driven out some years later by the Libyan National Army, forces loyal to Gen Khalifa Haftar who is allied to the eastern administration.
The powerful general said eastern officials were currently assessing damage caused by the floods so roads could be reconstructed and electricity restored to help rescue efforts.