Eighteen people perished when a wooden vessel carrying dozens of migrants capsized off the coast of Libya on Tuesday, while 64 people were rescued, the United Nations' migration agency said.

The vessel "capsized only a few hours into its journey due to high waves", the International Organization for Migration (IOM) said in a statement, adding that the accident had occurred off the coast of Surman, Libya.

"Among the survivors are 29 Sudanese men, one Sudanese woman, and one Sudanese child; 18 Bangladeshi men; 12 Pakistani men; and three Somali men," it said.

No information was yet available about the nationalities of those who died.

'World's deadliest migration corridors'

"This latest shipwreck is a stark reminder of the grave dangers faced by people undertaking perilous sea journeys in search of safety and opportunity," the IOM said.

It said the central Mediterranean route from northern Africa across to Europe remained "one of the world's deadliest migration corridors."

The agency said its Missing Migrants Project has documented 1,046 deaths and disappearances along that route so far this year, including 527 off the coast of Libya.

Tuesday's accident came after 40 migrants from Sub-Saharan Africa were found dead following a shipwreck off Tunisia last week.

IOM 'appeals for urgent action'

The IOM said it was working with local partners to ensure survivors of Tuesday's shipwreck received health assistance and access to essential services.

It appealed for "urgent action to prevent further tragedies at sea".