Following a criminal complaint by President Recep Tayyip Erdoğan, Ankara prosecutors have launched a probe into a former French diplomat for "calling for the assassination of the president," according to judicial and presidential sources.

Erdoğan early Monday filed a complaint against Philippe Moreau Defarges, who told French broadcaster BFM Business Saturday that in the wake of a referendum in favor of a presidential system, assassinating Erdoğan or Civil War were both options for Turkey.

The probe by the Ankara Chief Public Prosecutor's Office followed, according to a judicial source, who asked not to be named due to restrictions on speaking to the media.

Erdoğan's lawyer Hüseyin Aydın sent a four-page criminal complaint to the Ankara Public Prosecutor's Office accusing Defarges of "attempting assassination and assault," said an anonymous presidential source.

The source added, "In light of the terrorist groups which have been hosted by many European countries and all the incidents urging assassination of our president that took place there, it is clear that the suspect's remarks are far from a simple opinion, but are in fact an incitement."

Ahead of the April 16 referendum, rallies were seen in European cities in favor of terrorist groups such as the PKK. One, in Bern, Switzerland, featured a large banner saying "Kill Erdoğan" and a picture of a gun being pointed at the president's head.

Following a significant backlash, Defarges, a researcher at the French Institute of International Relations (IFRI), apologized for his controversial comments Sunday, calling them "inappropriate" and expressing his "deepest sadness."

Many complaints were also made on social media and to French authorities.