Istanbul, Sep 21 () - Four suspects, including a columnist for daily Bugün, have been arrested as part of an investigation into an alleged terrorist organization.

The 2nd Criminal Magistrate of Peace in Istanbul arrested columnist Gültekin Avcı and three police officers for “being a member of an armed terror group” on Sept. 20.

Three other police officers, who were detained with Avcı on Sept. 18 in the western province of İzmir, were released by the judge.

Avcı, a former prosecutor and also the lawyer of Samanyolu Medya Group chairman Hidayet Karaca, was detained as a part of an investigation into what state-run Anadolu Agency described as the “Pro-Fethullah Terror Organization/Parallel State Structure,” referring to the followers of U.S.-based Islamic scholar Fethullah Gülen, the government’s ally-turned-nemesis whose followers are believed to wield influence in the judiciary and the police.

In the summer of 2014, dozens of Turkish police officers, including high-ranking officers, were detained and accused of spying and illegally wire-tapping then-prime minister President Tayyip Erdoğan and his inner circle, in what the chief prosecutor said was a concocted probe of an alleged terrorist group named Selam Tevhid in a pretense to tap the phones of Erdoğan, a minister and the undersecretary of the National Intelligence Organization (MİT), Hakan Fidan.

The incident came months after a group of prosecutors launched corruption investigations into government figures in December 2013. The government described the prosecutors as “Gülenists” who had attempted to overthrow the government, before responding with massive reshuffling in the civil service, as well as criminal cases targeting them.