Eritrean refugees in Sudan accuse traffickers of abuse and torture.
There are calls for Sudan's government to do more - to stop human trafficking.
The African nation is used as a transit point by thousands of people from neighbouring Eritrea that are trying to reach the West.
They face a tough journey, often falling victim to smugglers on their way to the Libyan coast.
Al Jazeera's Hiba Morgan has more from Kassala, near the Sudan-Eritrea border.