Almost 1,000 migrants have died this year trying to cross the Mediterranean

The UN says there has been a rise in departures this year on the central Mediterranean route, an increase in the number of interceptions, and more arrivals.

A woman holds a baby as migrants and refugees from different African nationalities wait for assistance on an overcrowded rubber boat off the coast of Libya Source: AP

The deaths of 57 migrants off the Libyan coast brings the number of lives lost on the central Mediterranean crossing route this year to around 970, the United Nations said Tuesday.

At least 57 migrants drowned after their boat sank off Libya, said the UN's International Organisation for Migration - the latest tragedy on the dangerous Mediterranean Sea crossing to Europe.

Among those missing are at least 20 women and two toddlers, the IOM told reporters in Geneva.

The ship left the Libyan port of Khoms, some 120 kilometres east of the capital Tripoli, on Sunday, before it ran into trouble, took on water and sank.

"Local fishermen and the Libyan coastguard rescued 18 people from the water," said IOM spokesman Paul Dillon.

"Survivors told our staff who regularly respond to these heart-wrenching scenes that at least 57 people are missing.

"Our staff in Libya provided emergency medical assistance, food, water and comfort to the survivors, who are from Nigeria, Ghana and The Gambia.

NGO Proactiva Open Arms members recover a dead body of a migrant in the Mediterranean Sea Source: AP

"This latest tragedy pushes the 2021 death toll on the central Mediterranean route to roughly 970 men, women and children."

The IOM said there had been a rise in departures this year on the central Mediterranean route, an increase in the number of interceptions, and more arrivals.

"By advocating for better migration management practices, better migration governance and greater solidarity from EU member states, we can come up with a clearer, safe and humane approach to this issue that begins with saving lives at sea," said Mr Dillon.

"The time for a state-led approach to search and rescue is now, before more innocent lives are lost."

Returnees to Libya are typically taken to detention centres where there are documented cases of abuse and exploitation, with the IOM "deeply concerned" about the operations of such centres.

Mr Dillon said he was unaware of whether the 18 people rescued in the latest tragedy off the Libyan coast had been moved to detention centres.