Two Hundred Ennahdha activists were gathered in support of their leader Rached Ghannouchi on Tuesday in front of the headquarters of the anti-terror center in the Tunisian capital.
Ghannouchi, 81, has been under investigation since June amid allegations of corruption and money laundering linked to transfers from abroad to the charity Namaa Tunisia, affiliated with Ennahdha.
Supporters chanted Ghannouchi's name as he entered the building, making a V-sign with their fingers for victory and waving placards.
"Stop political trials", one read, written in both English and Arabic.
Earlier this month, a court ordered the freezing of the bank accounts of Ghannouchi and a dozen members of his family and his party -- including Jebali -- as part of this investigation.
In June, Ghannouchi was also handed a ban from travelling abroad as part of a separate investigation into high-profile political assassinations that rocked the country in 2013.
Ennahdha and Ghannouchi deny all charges against them.
As part of the same investigation, Tunisian authorities last month arrested former prime minister and one-time Ennahdha leader Hamadi Jebali for alleged money-laundering.
Jebali was later released, but is due to face questioning on the allegations on Wednesday.
Tunisia's long-running political crisis took a dramatic turn last July when President Kais Saied sacked the government, froze the Ennahdha-dominated parliament headed by Ghannouchi, and seized far-reaching powers.
Saied has put forward a draft constitution set for referendum on July 25, the anniversary of his power grab.
Opponents accuse him of waging political vendettas and dragging the country back to dictatorship, over a decade since its pro-democracy revolt sparked the Arab Spring uprisings.