Survivors have told the International Organization for Migration (IOM) how there are slave markets and private prisons all over Libya.

Mohammed Abdiker, IOM’s head of operation and emergencies, told The Guardian: “The situation is dire. The more IOM engages inside Libya, the more we learn that it is a vale of tears for all too many migrants.”

One survivor from Senegal spoke of how he was brought by smugglers across Niger in a bus to the southern Libyan city of Sabha, where he was due to risk a boat trip to Europe. When the middleman did not get his fee, the survivor was put up for sale along with other passengers.

He was taken to a prison where he worked without pay while the captors demanded 300,000 West African francs (about £380) before selling him on to a larger jail. Livia Manante, an IOM officer based in Niger, told The Guardian how migrants would be brought to a square where they were put up for sale.