Tunisian police arrested a political activist, a politically connected businessman and a member of the main opposition Ennahda party on Saturday, their representatives said.
The charges against the three, who were detained separately, were not clear. There was no immediate comment from the Interior Ministry.
A lawyer for Khayam Turki, the political activist, said the charges might relate to “suspicions of conspiracy against state security and the formation of an accord with the aim to change the nature of the state”.
Lawyer Ghazi Chaouachi told state news agency TAP that Mr Turki’s defence team would not be able to meet him until 48 hours after his arrest, which is the waiting time prescribed by law before charges can be confirmed in cases relating to terrorism.
Mr Turki, a former leading figure in the Ettakatol party, was arrested at his home on Saturday morning, according to his lawyers.
Construction magnate Kamel Eltaief was also arrested at his home, the businessman's lawyers said.
Mr Eltaief, 68, was once considered close to former president Zine El Abidine Ben Ali, who was toppled in a 2011 uprising.
Former senior Ennahda official Abdelhamid Jelassi was arrested after police searched his home and confiscated his mobile phone on Saturday evening, the party said.
Ennahda alleged that Mr Jelassi's arrest was intended to intimidate opponents of President Kais Saied, who dissolved the parliament last March after suspending the house and sacking the government in July 2021.
Mr Jelassi was an outspoken critic of Mr Saied, who introduced a new constitution last year in a move opposed by Tunisia's major political groups.
Mr Saied has said his actions were needed to save Tunisia from chaos, and has promised to uphold rights and freedoms won in 2011.
Several of Mr Saied's political opponents have been arrested or faced investigation in recent months.