A Tunisian anti-terrorism investigative judge decided to hold three prominent politicians and a high-profile businessman in pre-trial detention amid a continuing crackdown targeting opposition figures.
The four men are the first to face a judicial hearing among over a dozen leading figures critical of President Kais Saied, who have been detained this month.
The main charge against Abdelhamid Jlassi, a former senior official in the Islamist Ennahda party, former Finance Minister Khayam Turki, Republican Party leader Issam Chebbi and businessman Kamel Ltaif is conspiring against state security.
Lawyers for them and some of the others detained said they were boycotting the hearings because conditions for a fair trial had not been met.
Late on Friday, police also detained Ghazi Chaouachi, another prominent critic of Saied, his son said.
The arrests represent the biggest crackdown on opponents of Saied since he shut down the parliament and seized most powers in 2021 before moving to rule by decree and writing a new constitution that he passed last year in a referendum with a low turnout.
Activists and political parties, including Ennahda, which was the biggest in the parliament elected in 2019 and had played a role in successive coalition governments, have denounced Saied's moves as a coup.
They have warned that other moves by Saied, including taking ultimate authority over the judiciary and passing a law mandating prison for people convicted of posting false information online, augur a return to autocracy in Tunisia.
Saied has said his actions in 2021 were legal and necessary to save Tunisia from chaos and has denied that he will become a dictator.
He has called his opponents traitors, terrorists and criminals and said judges who fail to convict them should be considered accomplices.
The police, Interior Ministry and Justice Ministry have not commented on the detentions, which have also drawn in the head of Tunisia's main independent media outlet Mosaique FM.
Saied has said some of those detained are behind food shortages that economists blamed on a state finances crisis.
Police have also detained a senior figure in the powerful UGTT labour union and several members of a police union on separate charges.