A Tunisian investigative judge ordered on Thursday the imprisonment of Rached Ghannouchi, the leader of main opposition party Ennahda and a prominent critic of President Kais Saied, the politician's lawyer told Reuters.
Ghannouchi, who was arrested on Monday, is accused of plotting against internal state security and the decision to imprison him followed an investigation that lasted eight hours, she added.
Police have this year detained several leading political figures who have accused Saied of a coup for his moves to close parliament and rule by decree before rewriting the constitution.
"It was a ready decision to imprison Ghannouchi only because of Ghannouchi's expression of his opinion," lawyer Monia Bouali told Reuters.
Ghannouchi's official Facebook page published a comment by him after the judge's decision, which said: "I am optimistic about the future ... Tunisia is free".
The 81-year-old was the speaker of the elected parliament, which was shutdown in 2021 by Saied when he seized all powers.
Tunisian authorities on Tuesday banned meetings at all offices of Islamist party Ennahda and police closed the headquarters of the Salvation Front, the main opposition coalition.
Ennahda fears the move will pave the way for banning the party, the party said.
The US said Ghannouchi's arrest, the closure of Ennahda's headquarters and the banning of meetings by opposition groups represented a troubling escalation.
An interior ministry official said Ghannouchi had been arrested after "inciting statements".
Ghannouchi said in an opposition meeting last week that "Tunisia without Ennahda, without political Islam, without the left, or any other component, is a project for civil war."
The influential leader, who was in exile in the 1990s and returned during Tunisia's 2011 revolution that brought democracy, said those who "celebrated the coup are extremists and terrorists".
Ghannouchi has faced repeated rounds of judicial questioning over the past year on charges relating to Ennahda's finances and to allegations it helped Islamists travel to Syria for jihad, charges he and the party both deny.