New York - The UN Security Council must take stronger measures, possibly including sanctions, to put a stop to slave auctions in Libya, the French ambassador said on Monday.

France has requested an urgent meeting of the council for Tuesday, a week after the top UN body held a debate on human trafficking that touched on the abuse of migrants in Libya.

"We must go much further, much further in terms of saying 'no' to an unacceptable situation," French Ambassador Francois Delattre told reporters.

Asked whether sanctions were possible, Delattre said: "We are working on every conceivable measure to fight against this scourge. We don't exclude anything."

UN Secretary-General Antonio Guterres said last week he was horrified by footage aired by CNN showing an apparent live auction of African migrants to be used as farmhands.

The men were sold for as little as $400.

 'Egregious abuses' 

Guterres said the slave auctions were "among the most egregious abuses of human rights and may amount to crimes against humanity."

African leaders have expressed outrage over the images and called for an inquiry; Libyan officials say they have opened an investigation.

The reported slave auctions have raised questions about whether European Union migration agreements meant to curb Mediterranean crossings are instead turning human traffickers into slave traders as increasing numbers of migrants find themselves stuck in Libya, penniless, desperate and vulnerable.

Libya became an enormous transit hub for sub-Saharan Africans setting sail for Europe after the fall of dictator Moammar Gaddafi in 2011 tipped the country into chaos.

The European Union has been desperate to stem the migrant influx, as more than 1.5 million migrants have reached Europe since 2015.

Migration will dominate an EU summit with the African Union in Ivory Coast this week. Guterres will be in attendance.