The police searched Ghannouchi's house before taking him to an unknown location.
Several prominent political figures have been detained this year by the police for accusing Saied of carrying out a coup against the country's constitution.
Ghannouchi has faced multiple rounds of judicial questioning over the past year regarding Ennahda's finances and allegations that it aided militants traveling to Syria for jihad, but he and the party deny the charges.
No official statement has been released by the authorities regarding the detention of Ghannouchi yet. (ILKHA)