Abir Moussi, leader of one of Tunisia's main opposition parties, the Parti Destourien Libre (PDL), was arrested on Tuesday, her party's lawyer has said.
Tunisia: Opposition leader Abir Moussi arrested
Moussi was arrested outside the presidential palace in Carthage where she had come to lodge appeals against presidential decrees.
In a video post on PDL's Facebook page, the opposition leader said that the office of the President had refused to accept her appeal and to give her an acknowledgment of receipt.
Naoufel Bouden, PDL's lawyer, said the reasons for Moussi's arrest remain unknown.
"More details are expected this evening or tomorrow," he said.
Party members denounced the arrest as a "kidnapping" in statements to the Tunisian media. Crackdown on the opposition
Moussi, a former MP, is a fierce opponent of President Kais Said, as well as the Ennahdha Islamists. She is a supporter of late president Zine El Abidine ben Ali who was overthrown in 2011 during the first Arab Spring uprising.
The left accuses Moussi of seeking to re-establish a new dictatorship in Tunisia.
President Saied's government has cracked down on the opposition, imprisoning several prominent opposition figures since the beginning of February, including the leader of Islamo-conservative party Ennahdha, Rached Ghannouchi .
The opposition have decried Saied's presidency as authoritarian, with international bodies earlier this year also sounding the alarm over the country's turn towards autocracy.