According to the International Organization for Migration (IOM), the boat overturned in the perishingly cold waters of the central Mediterranean Sea, north of the coastal town of Zuwara last Friday.

It is just the latest deadly incident involving vulnerable people on the move who are frequently mistreated and trafficked by smuggling gangs that have flourished in Libya since the overthrow of President Muammar Gaddafi in 2011.

IOM said that the Libyan authorities rescued two Nigerian women from last Friday’s shipwreck; one said that her husband had drowned while the other reported that both her babies had died.

The survivors explained that the vessel had been carrying migrants and refugees from several African countries. It had set off from Zawiya at about 11pm on Thursday and began taking on water six hours later, before capsizing.

It is not yet known where the travellers were heading for, but many migrant and refugee boats leaving Libya set sail for the Italian island of Lampedusa, which is around 350 kilometres (220 miles) away from Zawiya. The open rubber dinghies they often sail in are totally unsuitable for such a journey, UN aid teams have often warned.

At least 375 people have been reported dead or missing in January alone in the central Mediterranean, according to IOM, missing migrants database. The UN agency warned that this is just the latest shipwreck to have happened amid severe winter weather, with many more tragedies feared unrecorded.

Smuggling and trafficking networks continue to profit from desperate people by sending them to sea in unseaworthy boats, IOM noted, as it renewed calls for greater international cooperation and safer, legal routes for migration.

So far this year, 781 migrants have been “intercepted and returned” to Libya, the UN agency said, with 244 taken back just last week. This compares with 27,116 last year including 1,314 reported deaths or missing persons.

Held in detention underground

“IOM does not consider Libya to be a safe port for migrants,” IOM insisted, after highlighting the dangers migrants continue to face following the discovery of more mass graves and detention sites in the east of the country.

“Investigations indicate that the victims had been held in captivity and subjected to torture to coerce ransom payments from their families,” IOM said in a statement, following a raid by the authorities on an illegal detention site in Ajdabiya.

In Kufra, authorities discovered an underground detention site three metres underground. A total of 221 migrants and refugees were released, including women, children and a one-month-old baby. "Initial information suggests that the migrants had been held for a prolonged period in grossly inhumane conditions," IOM said.

To help vulnerable people on the move, IOM supports voluntary flights home for foreign nationals. This includes one last week for Pakistani nationals who had reached Tripoli. In late January the agency helped 177 Nigerian migrants return home on another voluntary humanitarian flight

And in a bid to dismantle trafficking networks and support survivors, the UN agency works with national and regional authorities to strengthen cross-border cooperation.