LONDON — African migrants in Libya face “unimaginable horrors,” the United Nations human rights commissioner declared. “Despicable,” the chairman of the African Union called their treatment. Several African countries recalled ambassadors in protest. Rwanda offered the migrants assistance.

The mid-November broadcast by CNN showing what was described as African migrants being auctioned off at a Libyan slave market — for as little as $100 each, at black-market exchange rates — has set off an international firestorm. The response from the European Union, however, has been notably muted.

That may partly reflect the gratification among European Union officials over Italy’s success at reducing the influx of migrants across the Mediterranean. Italy has been helping Libyans stop them at sea or keep them in Libya, despite the dangers they face there.

Rights groups and other experts say the video of the slave market — although no surprise to many journalists or relief workers — is an uncomfortable reminder for Europe that its policies risk trapping the migrants in slave-like conditions.