Dozens of protesters gathered in front of the national union of journalists' headquarters in the capital Tunis on Thursday, chanting: "We are journalists, not terrorists" and "Freedom for the Tunisian press."
The rally follows a court's use of anti-terrorism laws on Tuesday to increase to five years a jail term handed to Khalima Guesmi, a journalist Mosaique FM radio station, after he appealed a one-year sentence delivered in November.
Guesmi was found guilty of having intentionally disclosed "information relating to operations of interception, infiltration, audiovisual surveillance or data collection," his lawyer said after the latest ruling.
"There is a frank and clear (political) orientation towards lockdown and repression, which targets disobedient media," said Mahdi Jlassi, president of the journalists' union.
"We are once again raising the alarm against the rollback of freedoms in this country and the legal proceedings targeting journalists, lawyers and trade unionists, and other people for comments, articles, or even a song," Jlassi added.
Around 20 journalists are currently being prosecuted for their work, he said.
On Monday, two Tunisian students were detained after posting a satirical song on social media that criticized police and laws against drug use.
Several local and international rights groups and trade unions on Tuesday warned "against the seriousness of the repressive direction of the current authorities" and called on activists and civil society "to mobilize to defend freedoms and human rights".
These groups have criticized the decline in civic freedoms in Tunisia since President Kais Saied launched a sweeping power grab on July 25, 2021.