Amnesty International has said Tunisian authorities “must come clean” over their alleged role in the illegal rendition of Algerian activist Slimane Bouhafs. The London-based watchdog demanded a thorough investigation be conducted into the disappearance of Bouhafs, an Algerian Christian convert who is formally recognized by the United Nations as a refugee.

“The Tunisian government shares responsibility for his fate and should come clean about its role in his abduction and return,” said Amna Guellali, Amnesty International’s Middle East and North Africa deputy director.

Bouhafs, who is being held in an Algerian prison on unknown charges, was snatched in the Hay Tahrir neighborhood of Tunis on Aug. 25 by three men in plainclothes and driven off in a black vehicle, according to eyewitness reports.

“Tunisia’s potential awareness of, cooperation in or acquiescence to his forcible transfer there despite his refugee status would constitute a grave violation of the principle of non-refoulement and international refugee law. Slimane Bouhafs’ recognition as a refugee by the UNHCR entails a finding that he has a well-founded fear of persecution on his return to Algeria,” the Amnesty statement read.