A former advisor to Tunisian President Moncef Marzouki has learnt he is being tried on charges of "denigrating" the army, after having accused senior officials of treason, his lawyer told AFP on Friday.

Ayoub Messaoudi has been charged with defamation and "denigrating a military institution," crimes which carry potential prison jails of two and three years respectively, Charfeddine El Kellil said, adding the verdict is due on Wednesday.

The accused himself only learnt that he was on trial on Thursday at Tunis airport, where he was presented with a ban on leaving the country.

Kellil was unable to give more details about the charges against his client that were filed by the army chief of staff, General Rachid Ammar, and Defence Minister Abdelkarim Zbidi.

Messaoudi had accused the two men in a television broadcast in July of "treason" for not having informed the president in advance of the extradition of former Libyan premier Baghdadi al-Mahmudi to Tripoli to face justice.

Prime Minister Hamadi Jebali ordered the transfer at the end of June, causing a political crisis within Tunisia's ruling coalition, led by Jebali's moderate Islamist Ennahda party.

Marzouki, who belongs to the centre-left Congress for the Republic, was furious with the decision, having always expressed doubts about the ability of the new Libyan regime to guarantee Moamer Kadhafi's last premier a fair trial.