CAIRO — A CNN report about the sale of African migrants as slaves in the North African nation of Libya has incited outrage in recent days, prompting a protest in central Paris, condemnation by the African Union and an official investigation.

Hundreds of protesters, mostly young black people, demonstrated in front of the Libyan Embassy in central Paris on Saturday — with some carrying a sign that said, “Put an end to the slavery and concentration camps in Libya,” and chanting, “Free our brothers!” — three days after CNN aired footage of migrants being auctioned off in the Libyan capital, Tripoli.

“We have to mobilize — we can’t let this kind of thing happen,” one of the protesters told the television station France 24. “Did we really need to see such shocking pictures before taking a stand? I don’t think so.”

French police officers fired tear gas to disperse the rally, which had turned violent.

Moussa Faki Mahamat, the chairman of the African Union Commission and the foreign minister of Chad, issued a statement after the rally, calling the auctions “despicable.” He urged the African Commission on Human and Peoples’ Rights to assist the Libyan authorities with the investigation that they opened in response to CNN’s report.