Ben Mbarek, co-founder of the National Salvation Front opposition alliance, went on hunger strike on October 28 to protest his detention, which began in February 2023.

In April, he was sentenced to 18 years behind bars on charges of “conspiracy against state security” and “belonging to a terrorist group” in a mass trial criticised by rights groups.

Ben Mbarek’s sister Dalila Msaddek, who is a lawyer, said she did not recognise him when she visited him in jail in northern Tunisia.

“He was moving with difficulty. He looked pale and couldn’t speak,” a tearful Msaddek said in a video Wednesday.

“He wants to leave… He is overwhelmed. The feeling of injustice is strong,” she added.

Rights groups have warned of a sharp decline in civil liberties in the North African country since a sweeping power grab by President Kais Saied in July 2021.

Many Saied critics have been prosecuted and detained under Decree 54, a law he enacted in 2022 to prohibit “spreading false news”.

Ben Mbarek was also convicted under the decree in a separate case.

His defence lawyer Samir Dilou visited him on Tuesday.

“His condition is worrisome,” he told AFP on Wednesday, calling for Ben Mbarek to be “provided with the necessary care”.

Fellow defence lawyer Ayachi Hammami called for the opposition figure’s “immediate transfer” to hospital in a video posted on Facebook.

“His condition is alarming,” he said, adding that they held the prison administration, justice ministry and president “responsible for anything that might happen to him”.

Prison authorities denied in a statement that the health of certain unnamed prisoners had deteriorated because of a hunger strike.

“The health of the individuals concerned is normal and stable, according to the results of medical examinations and checks carried out daily and continuously by medical and paramedical staff,” the general prison committee said.