A Tunisian court overturned on Wednesday a journalist's prison sentence for revealing information about the security services, his lawyer said, paving the way for a retrial.

Khalifa Guesmi, a correspondent for Tunisia's most popular radio station Mosaique FM, was convicted in November and sentenced to a year in prison, later upgraded to five years on appeal.

The Court of Cassation "invalidated the five-year judgement and ordered it to be reviewed on appeal," Guesmi's lawyer, Rahal Jallali, told AFP.

He said Guesmi should be released by Thursday morning.

The journalist remains under prosecution according to his lawyer, under Article 34 of the anti-terrorism law which "punishes with 10 to 20 years' imprisonment" anyone who publishes information "for the benefit of a terrorist organisation".

Journalists and civil society representatives gathered in Tunis on Wednesday to show support for Guesmi and to call for his immediate release.

Local and international NGOs have launched several calls for his release and condemned the five-year prison sentence as "a sham verdict" and "a major setback for the judicial system".

They have criticised what they say is a marked decline in press freedom in Tunisia since President Kais Saied seized full control of the country in July 2021.

Jailed since September 3, Guesmi was found guilty of "participating in the intentional disclosing of information related to interception, infiltration, and audiovisual surveillance or the data collected therein".

He was held for a week in March 2022, after Mosaique FM published on its website information about the dismantling of a "terrorist cell" and the arrest of its members.