The organization published a 79-page report Tuesday which it says proves traffickers since 2010 have tortured Eritreans for ransom. Victims told a Human Rights Watch security officer neighboring Sudan and Egypt played a role in the atrocities as well.
Relatives of abuse victims were forced to listen to what Human Rights Watch said was torture in an effort to collect ransom money.
"Both Egypt and Sudan need to put an end to torture and extortion of Eritreans on their territory, and to prosecute traffickers and any security officials colluding with them," Gerry Simpson, author of the report, said in a statement from Berlin.
The rights group said more than 200,000 Eritreans have tried to flee their country because of repressive government policies. Eritrean border guarders have shoot-to-kill orders to prevent people from leaving the country without permission, the rights group said.
Simpson said it may be too late for victims who have already "gone through hell" but international pressure may help address the impunity.