More than 5,300 people are believed to have died after floods in the Libyan city of Derna, an official has said.
"The sea is constantly dumping dozens of bodies," Hisham Chkiouat, a minister in Libya's eastern administration said.
There have been desperate 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 - but hope is waning and the death toll is still expected to rise further.
Officials say at least 10,000 people are missing, while 30,000 people are estimated to have been displaced, the United Nations' International Organization for Migration (IOM) in Libya said on Wednesday.
Morgues and hospitals have been overwhelmed with bodies.
Libyan doctor Najib Tarhoni, who has been working in a hospital near Derna, said more help 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."
There is also an urgent need for specialised forensic and rescue teams and others who specialise in recovering bodies, the head of the Libyan doctors' union Mohammed al-Ghoush told Turkish media.
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".
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."
Taha Muftah, a photojournalist in Derna, said experts had raised the alarm about the dam since 2011 "but nobody did anything about it".
He told the BBC's Newshour programme that the dam collapse sounded "like an air strike".
"The water now has stopped and what is left is only the rubble, and the people who were taken by the flood are under the water," he said.
A number of elite footballers have died, according to the Libya Football Federation (LFF).
It released the names of four players who were killed: Shaheen Al-Jamil, Monder Sadaqa and brothers Saleh Sasi and Ayoub Sasi.
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.