In a significant escalation of legal challenges, prosecutors in Ankara have leveled fresh espionage charges against Istanbul’s imprisoned mayor, amplifying the judicial scrutiny faced by the prominent opposition figure who is considered a key contender against President Recep Tayyip Erdogan.

The latest allegations against Mayor Ekrem Imamoglu follow an investigation initiated last week. This probe examines potential connections between his political campaign and a businessman who was detained in July on accusations of conducting intelligence operations for foreign entities.

Alongside Imamoglu, his former campaign manager, Necati Ozkan, and journalist Merdan Yanardag have also been implicated in these charges.

According to the state-run Anadolu Agency, Imamoglu, currently held in pretrial detention over separate corruption allegations, is accused of using personal data from Istanbul residents to allegedly secure international financial support for his campaign efforts.

Imamoglu has vehemently denied these charges, dismissing them as “nonsense” in a statement shared on social media platforms.

“Even the claim that I burned down Rome would have been more credible than this nonsense,” Imamoglu said. “Our struggle against this mindset that has sworn to ruin our nation’s future has now grown even stronger.”

Hundreds of supporters had rallied outside Istanbul’s main courthouse on Sunday as Imamoglu was questioned by prosecutors. It was the first time Imamoglu had left Istanbul’s Marmara Prison, on the outskirts of Istanbul, in seven months.

Critics view Imamoglu’s arrest — along with those of other mayors from the main opposition Republican People’s Party, or CHP — as part of a broader crackdown on the opposition, which made significant gains in last year’s local elections. Several CHP-run municipalities have faced waves of arrests throughout the year.

Imamoglu’s arrest in March sparked nationwide protests. Erdogan’s government insists that Turkey’s judiciary is independent and that the investigations are strictly focused on corruption.