Abdul Aziz Naji was transferred from the military prison in Cuba to Algeria against his will, having said he feared persecution. A US based rights group said Wednesday he had gone missing and could be in secret detention.

US President Barack Obama has made a commitment to close down the Guantanamo Bay prison and any evidence that former detainees are mistreated after they are released and sent home could make it harder for him to meet that target.

"It is out of the question that this person has been detained in Algeria," said Farouk Ksentini, chairman of Algeria's National Consultative Commission for the Promotion and Protection of Human Rights, a state body.

"I formally deny this information, which in my view does not make any sense," Ksentini told Reuters, though he added that he did not know Naji's whereabouts.