CAIRO — Farah Hamed, a Sudanese refugee from the war-torn province of Darfur, was startled when he heard a loud knocking on his apartment door in Cairo in July. Too scared to open the door, he looked through the peephole to see who it was. He said that is when he saw the man from Sudan’s National Intelligence and Security Service who had arrested and tortured him in Sudan in 2010. Backing away, Hamed instructed his son to be quiet and then waited silently until the man finally left.

“A year before he came to my home, I saw my torturer in a market in Cairo,” said Hamed, a 47-year-old man with a nest of wrinkles around his eyes. “He approached me and said, ‘Even if you die in Egypt, I will pull your corpse from the ground and kill you again.'"

Fear of the Sudanese intelligence service has dissuaded thousands of Sudanese refugees in Egypt from returning to their villages in Darfur. The United Nations has nonetheless facilitated the voluntary repatriation of Sudanese nationals living elsewhere in Africa in recent weeks.

By Jan. 7, 1,494 Sudanese nationals had returned to South Darfur, ending 10 years of asylum in the Central African Republic. And in October, Sudanese refugee leaders in Chad had visited Darfur to assess the prospect of returning. But those in Egypt insist they will be arrested or killed if they turn back. The Sudanese intelligence service, they say, is already threatening political activists and religious converts in exile.