France on Wednesday called an emergency meeting of the UN Security Council over slave-trading in Libya as President Emmanuel Macron blasted the auctioning of Africans as a crime against humanity.
"France decided this morning to ask for an urgent meeting of the United Nations Security Council to discuss this issue," Foreign Minister Jean-Yves Le Drian told parliament.
"We are doing it as a permanent member of the Security Council. We have this capability and we are using it."
Macron said the auctions, captured in shocking footage aired by US network CNN, were "scandalous" and "unacceptable".
"It is a crime against humanity," he said after meeting with African Union chief Alpha Conde in Paris.
"I hope we can go much further in the fight against traffickers who commit such crimes, and cooperate with all the countries in the region to dismantle these networks."
CNN aired footage last week of an apparent auction where black men were presented to North African buyers as potential farmhands and sold off for as little as $400.
The video prompted a wave of condemnation, including from African stars such as Ivorian football player Didier Drogba.
But the European Union -- where Macron is trying to carve out his influence -- has also been criticised for cooperating with the Libyan coastguard in seeking to block migrants from leaving.
The UN this month deplored an EU policy of helping the Libyan authorities intercept migrants trying to cross the Mediterranean and return them to "horrific" prisons in Libya.
Guinean president Conde on Wednesday also criticised Europe's cooperation with the Libyans.
"The refugees are living in extremely bad conditions," he said. "Our European friends were not right to ask Libya to keep immigrants (in detention)."
The AU leader said he was "in contact with all leaders", adding: "We are trying to find a solution, even if it means bringing all of our citizens home."
UN human rights chief Zeid Ra'ad Al Hussein this month accused the international community of turning a "blind eye to the unimaginable horrors endured by migrants in Libya" and called the EU's policy "inhuman".
AFP spoke to a number of black African men in Cameroon this week who reported being slaves in Libya, which descended into civil war after the Western-backed overthrow of dictator Moamer Kadhafi in 2011.
"It was total hell," said Maxime Ndong, one of 250 migrants who arrived in Cameroon on Tuesday night on a plane chartered by the International Organization for Migration to take people home.
"There is a trade in black people there. People who want slaves... come to buy them," he told AFP.
"If you resist, they shoot at you. There have been deaths," added Ndong, who spent eight months in Libya.
Another migrant, 22-year-old Sanogo, said he had been caught by people who said they were police before being sold to a slave trader. He was then forced to work on a tomato farm.
Macron has been pushing for a solution to the chaos in Libya, organising a meeting between its rival leaders in Paris in July at which they agreed a conditional ceasefire and elections for next year.