The African Union on Friday called for Libyan authorities to investigate "slave markets" of black Africans operating in the conflict-torn nation, following the release of shocking images showing the sale of young men.
The demand followed the release of CNN footage of a live auction in Libya where black youths were presented to north African buyers as potential farmhands and sold off for as little as $400.
Guinean President Alpha Conde, who is also chairman of the African Union, demanded an inquiry and prosecutions relating to what he termed a "despicable trade ... from another era."
Meanwhile, Senegal's government, commenting on Facebook, expressed "outrage at the sale of sub-Saharan African migrants on Libyan soil," which constituted a "blight on the conscience of humanity."
African migrants from nations including Guinea, Senegal, Mali, Niger, Nigeria and Gambia make the dangerous crossing through the Sahara to Libya with hopes of making it over the Mediterranean Sea to Italy.
But testimony collected by AFP in recent years has revealed a litany of rights abuses at the hands of gang leaders, human traffickers and the Libyan security forces, while many end up stuck in the unstable north African nation for years.
More than 8,800 stranded migrants have been returned home this year, according to the International Organization for Migration, which is also amassing evidence of slavery.
Conde further appealed for the Libyan authorities to "reassess migrants' detention conditions" following revelations about squalid jails and detention centers that await migrants who are caught trying to reach the coast.
"These modern slavery practices must end and the African Union will use all the tools at its disposal," Conde added.
Libya has opened an investigation into the practice, CNN reported Friday, and pledged to return those taken as slaves to their countries of origin.