A Tunisian court on Friday handed down a 22‑year prison sentence in absentia to former President Moncef Marzouki, a fierce critic of President Kais Saied, on charges of undermining state security, raising the opposition's fears of an escalating crackdown against critics.

Marzouki, who was president from 2011 to 2014, accuses Saied of establishing an authoritarian regime after dismissing parliament and ruling by decree since he seized almost all powers in 2011.

Saied defends his actions as necessary steps to stabilise Tunisia.

This is the third ruling against Marzouki, after a court ruled last year to imprison him for eight years and four years before that in various other cases.

Commenting on the ruling, Marzouki said from his exile in Paris: "I say to these judges: your rulings are invalid, and you are invalid ... you will be tried soon".

"Democracy will return", he added.

Earlier on Friday, another court sentenced Sahbi Atig, a senior official in Ennahda, the country's main opposition party, to 15 years in prison on charges of money laundering, his lawyer said.

The 15-year sentence was shorter than some sentences handed down recently. In April, a court sentenced a string of opposition leaders, businessmen and lawyers to prison terms of up to 66 years, on conspiracy charges.

Most of the leaders of political parties in Tunisia are in prison, including Abir Moussi, leader of the Free Constitutional Party, and Rached Ghannouchi, the head of Ennahda - two of Saied's most prominent opponents.