İlhan Toprak, Anadolu news agency’s reporter at the presidential palace was detained over his alleged use of ByLock, on Saturday.
Turkish government claims that ByLock is the top communication tool among the members of the Gülen movement, accused to be behind the July 15 coup attempt.
Tens of thousands of civil servants, police officers and businessmen have either been dismissed or arrested for using ByLock. Critics blast the government for detaining thousands simply for using a mobile application.
According to Turkish media, Toprak was taken under custody immediately after he returned from Pakistan where he accompanied President Recep Tayyip Erdoğan in his trip to the Asian country, on Saturday.
Turkey already keeps more than 150 journalists under arrest with many also being under detention.