Turkey accuses Gulen of masterminding last year's failed military coup. Gulen denies involvement.

Police carried out raids in Istanbul to detain the suspects who allegedly used an encrypted messaging app that authorities say was favored by Gulen's followers to communicate with each other. Anadolu Agency said they are suspected of "membership in a terror organization."

Nine people have been detained so far, including Burak Ekici, an editor for the opposition Birgun newspaper, Anadolu said.

More than 50,000 people, including journalists, have been arrested since Turkey embarked on a wide scale crackdown in the aftermath of the July 15, 2016 coup attempt. More than 110,000 people have also been dismissed from government jobs.