A Tunisian judge on Thursday ordered the imprisonment of Abir Moussi, a prominent opponent of President Kais Saied, two days after she was arrested at the entrance to the presidential palace.
The case concerning Ms Moussi continued for hours while her supporters gathered, with slogans demanding her immediate release and some against Mr Saied.
Her lawyer, Nafaa Laaribi, confirmed the judge's ruling.
The court's chief investigating judge ordered a detention warrant after the Tunis Appeals Prosecutor opened an investigation "into her October 3 actions, which constitute several crimes punishable by law".
No other details were immediately available.
Ms Moussi, who leads the Free Constitutional Party, was "kidnapped" from outside Carthage Palace, according to her assistant.
Her party said her phone was seized and she was taken to an unknown location before arriving at the police station.
Relatives of detained opposition lawyers and politicians have launched a bid at the International Criminal Court to investigate claims of political persecution and human rights breaches under Mr Saied.
On Monday they said there had been a "major increase" in "repression and and mass human rights violations" at the behest of Mr Saied.
Among the group is Yusra Ghannouchi, daughter of former parliamentary speaker Rached Ghannouchi who went on hunger strike at the weekend in support of prominent opposition figure Jaouhar Ben Mbarek.
Ms Moussi said she visited the presidential registry earlier on Tuesday to file an appeal against a presidential decree before local elections this year.
She then staged a sit-in outside Carthage Palace after the rejection of her appeal.
Ms Moussi is one of dozens of opposition officials to be detained this year.
The judiciary has detained media, business and judicial officials with ties to the opposition, who Mr Saied has called "terrorists" plotting against the state.
