"They were unable to confront a major political opponent in freedom through the ballot box. So they tried to accuse Ennahda of terrorism," Ghannouchi said as he left the court, waving to supporters from the sunroof of a car.
The police or other authorities have not publicly commented on the case.
Police had questioned Ghannouchi for more than 12 hours overnight over accusations that he had helped Tunisians travel to Syria for jihad during the Islamic State crisis last decade.
Ghannouchi was also investigated earlier this summer regarding accusations of money-laundering, which he denied.
The 81-year old head of the Islamist Ennahda party, who was also speaker of the dissolved parliament, has asserted all the charges are politically motivated.
Another senior Ennahda figure, former Prime Minister Ali Laareyedh, will face a hearing later on Wednesday over the same accusations, which he also denies.
Ennahda has accused police of using the investigation to intimidate them because of the party's opposition to President Kais Saied's seizure of broad powers and shutdown in July 2021 of the elected parliament.
President Saied's critics accuse him of a coup for seizing most powers last year and moving to one-man rule, and of dismantling the democracy won in the 2011 revolution that triggered the Arab Spring uprisings