(CNN) - The UN secretary-general said Monday he is "horrified" at reports showing African migrants sold as slaves and called for immediate investigations.
The reports demonstrate some of "the most egregious abuses of human rights" and may amount to crimes against humanity, Secretary-General António Guterres said.
"I abhor these appalling acts and call upon all competent authorities to investigate these activities without delay and to bring the perpetrators to justice," Guterres said. "I have asked the relevant United Nations actors to actively pursue this matter."
Urging the international community to unite on the issue, the UN chief called on all countries to adopt the UN Convention against Transnational Organized Crime and its protocol on human trafficking.
He further said the Libya story provides a reminder of the need to manage migration flows in a humane manner that addresses the root causes, increases opportunities for legal migration and cracks down on smugglers.
After obtaining footage of a human auction in Libya, a CNN team traveled in October to that country to investigate. It saw a dozen men sold at an auction outside of the capital, Tripoli -- some for as little as $400. The crew was told of auctions taking place at nine locations in the country.
Libyan authorities have launched a formal investigation into the auctions. It is being overseen by the government's Anti-Illegal Immigration Agency.
"Priorities of the investigation are not only to convict those responsible for these inhumane acts, but also to identify the location of those who have been sold in order to bring them to safety and return them to their countries of origin," Anes Alazabi, an official with the agency, told CNN.
News of the auctions spurred protests outside of the Libyan Embassy in Paris, and French soccer star Paul Pogba raised the issue after scoring a goal for his club, Manchester United, on Saturday, putting his wrists together as if they were handcuffed.
"My prayers go to those suffering slavery in Libya. May Allah be by your side and may this cruelty come to an end!" Pogba wrote later on Instagram.
The United Nations estimates there are 700,000 migrants in Libya, and for years those who have crossed the Mediterranean have shared stories about beatings, kidnapping and enslavement.
Correction: This story has been revised to state that UN Secretary-General António Guterres made his comments Monday, not Sunday.
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