Thirty police officers were detained Thursday in Istanbul-based operations held across 22 Turkish provinces against the Fetullah Gulen Terrorist Organization or FETÖ, also known as the "parallel state".
The Istanbul Chief Public Prosecutor's Office issued an arrest warrant for 41 police officers, including a number of police chiefs.
One of the suspects had already been arrested in a previous anti-parallel state operation, while three others are currently at large, police said.
The suspects are accused of being behind the 2011 death of journalist Haydar Meriç, who reportedly was about to write a book critical of Gülen, who is based in the U.S. and wanted by Turkey for extradition.
The suspected police officers were allegedly tapping the journalist, who reportedly belonged to a leftist terrorist group.
Meriç was kidnapped in May 2011 in Turkey's central Kırklareli province, and his body was found the next month in the northwestern Düzce province, according to the prosecutor's office.
The detained police officers are also suspected of having covered up evidence of the journalist's murder.
Police continue to investigate the incident.
The Fetullah Terrorist Organization is led by U.S.-based cleric Fetullah Gülen, who is accused of attempting to overthrow the Turkish government through a network of supporters, known as Gülenists, within state institutions.