The victims were among a group of around 200 Eritreans, Ethiopians and Somalis who escaped on 23 May.
UNHCR spokesperson William Spindler told journalists in Geneva that survivors described how “people were shot while trying to escape, and during attempts to recapture them” in Bani Walid, nearly 200 kilometres south of the capital Tripoli.
It is one of many areas of the North African country that have been under the control of armed groups since the overthrow of the late President Muammar Gaddafi in 2011.
The survivors also spoke of “torture, abuse and exploitation at the hands of traffickers”, Mr. Spindler said, adding that some had been detained for up to three years.
According to UNHCR, the survivors have been transferred to an official detention centre closer to Tripoli, where they have been given relief items and psychosocial support.
The agency is in discussion with the Libyan authorities to build an open reception centre for migrants and refugees, but for the time being, detention is “mandatory”, Mr. Spindler said:
“The issue in Libya is that there are, so far, no places where people who are found in this situation can be taken”, who don’t fall into the migrant category, he said, adding that “detention is mandatory for all undocumented people who find themselves in the country, whether they are refugees or economic migrants”.
Among the survivors are “a large number of unaccompanied children” and UNHCR is working to identify the most vulnerable who may need international protection.
Mr. Spindler described the incident as “the latest horror story coming out of Libya” where people are being held by traffickers in horrific conditions and sold into a life of what is, in effect, modern-day slavery.
But he said that apart from the extraordinary circumstances of the escape, the deaths were “not an isolated case”, and warned that many refugees and migrants may still be hiding, or in captivity, in or near Bani Walid.
The oil-rich State has attracted nationals seeking work from neighbouring countries for decades, and more recently those fleeing war and persecution from the African continent and beyond.
Thousands more are in facilities run by armed groups, some of which are affiliated with the State, the study found.