TUNIS - Tunisia has confiscated the passport of a man suspected of being an Islamist militant who once served as Osama bin Laden's bodyguard to prevent him returning to Germany, a judiciary official said on Friday.Germany deported Sami Aidoudi last month but a German court on Wednesday demanded his return, saying he may face torture in his native Tunisia, a concern the North African country denies.Tunisian authorities initially detained Aidoudi after Germany deported him last month. They released him after two weeks for lack of evidence but have barred him from leaving the country pending the outcome of an investigation."The investigation is ongoing... His passport has been confiscated by a court (in case he gets charged)," said Sofian Sliti, spokesman of Tunisia's anti-terrorist judiciary body."If there was a request from German authorities (to Tunisia) to hand him over it should come via diplomatic channels," he added.A spokesman for the German government said Berlin was in constant contact with Tunis via its embassy there and would continue to discuss the case.German opposition and rights groups criticized the decision to deport Aidoudi, saying he could face torture in his home country and citing a German court decision that he should be allowed to stay.Aidoudi - referred to only as Sami A. in Germany - applied unsuccessfully for asylum there in 2006. German Interior Minister Horst Seehofer, who has taken a tough line on immigration, accused him in May of having been bin Laden's bodyguard and said he should be deported.Aidoudi always denied the allegation but was arrested in June and deported a month later on July 13.Germany's interior ministry later denied opposition accusations that it had pressured authorities in the state of North Rhine-Westphalia to accelerate the deportation.Tunisia has won praise for its transition since authoritarian leader Zine al-Abidine Ben Ali was ousted in 2011.It has agreed on a constitution guaranteeing fundamental rights, held elections and largely avoided the political turmoil seen elsewhere in the region.Human rights groups have on occasion accused members of security agencies of abuses against Islamist suspects - accusations denied by the authorities.