The source, who spoke on condition of anonymity due to restrictions on talking to media, told Anadolu Agency that the arrest of Kemal Kilicdaroglu's science, technology and communication advisor occurred in Ankara.
According to Istanbul’s Chief Public Prosecutor's Office, orders to arrest the academic Fatih Gursul had been issued Tuesday.
Gursul, who had offered his services to Kilicdaroglu in 2013, had also suspended from Istanbul University in August amid a national probe into the FETO coup attempt.
A CHP official who spoke on condition of anonymity said that the arrest was related to the alleged use of a messaging app linked to Turkey’s July 15 coup plot.
The ByLock smartphone app is believed to have been cracked by Turkish security agencies months before the coup, allowing them to identify tens of thousands of apparent FETO supporters.