The United Nations aid chief said on Friday that Libya needed equipment to find people trapped in sludge and damaged buildings after floods that have killed thousands, as well as primary health care to prevent a cholera outbreak among survivors.

"Priority areas are shelter, food, key primary medical care because of the worry of cholera, the worry of lack of clean water," Martin Griffiths told a UN briefing in Geneva.

He said the UN humanitarian office had sent a disaster coordination team of 15 people to Libya who had been redeployed from Morocco, which suffered an earthquake last week.

Swathes of Derna, the centrepoint of the destruction in the country's east, were obliterated by flooding on Sunday night, bringing down whole buildings while families were asleep.

Griffiths said that a suggestion by the mayor of Derna to create a maritime corridor to deliver aid could be a viable option given that the city is on the Mediterranean Sea.

"You still keep coming in from the land, you're finding the people who are fleeing south, fleeing south from Derna, towards aid, away from the cities, so you need to support them as well," he said.

"But certainly, adding the maritime option makes complete sense."