Three Libyans killed a Nigerian man by setting him on fire in Tripoli, the interior ministry said on Wednesday, in what a UN agency described as "another senseless crime against migrants in the country".
The Tripoli-based interior ministry said in a statement it had arrested the three suspects in the case, adding that they had used petrol to set the victim on fire at a factory.
Federico Soda, Libya country chief for the International Organisation for Migration (IOM), a UN migration agency, said those responsible must be held accountable.
There are half a million migrants in Libya according to IOM, some of them having worked in the oil producing country before it descended into chaos and warfare, others attempting to travel through it to Europe.
The IOM and the UN refugee agency UNHCR have both repeatedly said that Libya should not be classified as a safe port for migrants.
Thousands have attempted the perilous sea crossing to Europe this year, with hundreds drowned in ship wrecks.
In July, three migrants from Sudan were shot dead by Libyan authorities while trying to flee detention after they were disembarked in Khums.
In May, some 30 mostly Bangladeshi migrants were shot dead in a southern desert town after being abducted by a local gang, Bangladesh and the Libyan interior ministry said at the time.