Rached Ghannouchi, President Kais Saied’s 81-year-old rival, was ordered to appear at a police station in the capital on Tuesday, Ennahdha spokesman Imed Khemiri told journalists, calling it “a new attack on political leaders.”

Khemiri said the party “does not know the reasons for this summons, but it is part of an enquiry after a complaint was lodged by an unknown person.”

A party official said the complaint came from a member of Tunisia’s powerful police unions, who “claimed to have a recording of a telephone call” involving Ghannouchi.

The latest in a string of legal woes facing Ghannouchi comes a year and a half after Saied launched dramatic measures, freezing and later scrapping the legislature Ghannouchi headed.

Several prominent critics have since faced trial in military courts.

Many of the enquiries have targeted Ennahdha, which has been a major political force in Tunisia’s parliament and most governments since the 2011 revolution.

Ghannouchi was questioned by an anti-terror judge in November over alleged involvement in helping Tunisians traveling to fight for terrorist groups in Iraq and Syria.

Prior to that he was interrogated over alleged money laundering in relation to foreign donations for an Ennahdha-linked charity.

Zeineb Brahmi, the party’s legal chief, quipped that “we don’t know whether the investigation this time will be over plotting against state security, financial corruption or terrorism.”

Khemiri accused authorities of “harassing” Saied’s rivals saying it had become “very easy” for authorities to prosecute politicians.

“All it needs is a complaint to be lodged for the police to open an investigation, with zero verification of its basis,” he said.