Tunisian security forces have detained a senior official from the biggest party in the suspended parliament for the first time since President Kais Saied came to power in July, the party said.
Ennahda, which accuses Mr Saied of a coup for freezing the parliament and accumulating power, said plainclothes agents seized Noureddine Bhairi on Friday morning and took him away, Reuters reported.
Ennahda called the arrest a dangerous precedent. The government and security services were not immediately available to comment, according to Reuters.
Ennahda, an Islamist party that has the largest number of seats in the suspended parliament, has been a member of successive coalition governments since the revolution.
But as Tunisia's economy stagnated and its political system ground to a halt in recent years, support for the party has waned.
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Since Mr Saied's came to power in July, several senior politicians and business leaders have been subject to legal prosecution, often involving accusations of corruption or defamation.