At least 20 more migrants have died in a shipwreck hours after 74 others were drowned in a separate accident off the coast of the Libyan port of Khoms, rescuers say.

Refugees and migrants are seen onboard the former fishing trawler Golf Azzurro of the Proactiva Open Arms in central Mediterranean Sea August 17, 2017.
Refugees and migrants are seen onboard the former fishing trawler Golf Azzurro of the Proactiva Open Arms in central Mediterranean Sea August 17, 2017. (Reuters)

A shipwreck off the Libyan coast has killed 20 people just hours after news of a separate incident in which at least 74 migrants died.

Teams of the Doctors Without Borders (MSF) in northwestern coastal city of Sorman "assisted three women as the lone survivors of another shipwreck where 20 people drowned," the group said on Thursday on Twitter.

"Rescued by local fishermen, they were in shock and terrified; they saw loved ones disappear beneath the waves, dying in front of their eyes," it added.

Earlier on Thursday, the UN's International Organization for Migration reported "a devastating shipwreck which claimed the lives of at least 74 migrants today off the coast of Khoms," a port city 120 kilometres east of the Libyan capital Tripoli.

It said that 47 survivors had been brought back to shore and 31 bodies retrieved, adding that the boat was reported to be carrying more than 120 people.

READ MORE: UN: Dozens of migrants drown after boat breaks down off Libya coast

Corridor to reach EU

The IOM said that so far this year, at least 900 people had drowned in the Mediterranean trying to reach European shores – some due to delays in rescue.

More than 11,000 others have been returned to Libya, it said, "putting them at risk of facing human rights violations, detention, abuse, trafficking and exploitation".

Human traffickers have taken advantage of persistent violence in Libya since the 2011 overthrow of late Libyan leader Muammar Gaddafi, turning the country into a key corridor for migrants fleeing war and poverty in desperate bids to reach Europe.

While many have drowned at sea, thousands have been intercepted by the Libyan coastguard, which has been backed by Italy and the EU, and returned to Libya.

They mostly end up in detention, often in horrific conditions.

READ MORE: Almost 100 refugees evacuated from Libya to Italy

Source: AFP