Farid said the warring factions were stealing food aid and selling it.
"That's why so many are dying in al-Fashir. They are starving."
On his way from Sudan, Farid passed through Kufra, an isolated area in southeastern Libya where mass graves containing the bodies of scores of migrants have been discovered. Kufra is controlled by rival armed groups, representing the Arab Zway majority and the ethnic Tebu minority.
When he arrived outside Kufra, Farid found hundreds of Sudanese refugees crowded by the roadside seeking assistance. He was offered a mattress and some food by Libyan authorities, but in return he was forced to work long hours collecting plastic waste for recycling. He was paid nothing.
When he complained, he was told that if he caused any problems, he would be sold to a rival militia or worse.
"Kufra is a tribal area. And we are slaves in their land," Farid said, his voice trembling. "They make us fight for them or sell us into forced labour. If you refuse, they can take your organs and bury you by the road."
'SNAKES AND LADDERS'
According to the UN refugee agency, there are more than 210,000 Sudanese refugees in Libya, accounting for 73% of all refugees. Hundreds more arrive each day.
Since the fall of Muammar Gaddafi in 2011, Libya has been torn by factional conflict and is a major route for migrants fleeing war and poverty.
Most Sudanese arrive through Kufra, then move north to cities like Ajdabiya in the east or the coastal capital Tripoli.