Five of the 27 suspects detained for their alleged involvement in establishing an armed terrorist organization and fabrication of crimes on behalf of a terrorist organization were released on Monday.

The released suspects, Elif Yılmaz, Ebru Şenvardar and Naci Çelik Berksoy, worked on a TV series known as "Tek Türkiye" that broadcasts on Samanyolu TV, which is allegedly linked to the U.S.-based movement leader Fethullah Gülen. Gülen-linked daily Zaman writer Ahmet Şahin and former Gülenist Hüseyin Gülerce were also released.

Prosecutor Hasan Yılmaz began taking the testimony of the 22 other detainees, including the editor-in-chief of Turkey's Zaman daily Ekrem Dumanlı, chairman of Samanyolu Media Group Hidayet Karaca, producer Salih Aslan and director Engin Koç of Samanyolu TV, and Makbule Cam Alemdağ, a scriptwriter of a TV series that is aired on the network.

All those detained are allegedly linked with Gülen and the Gülen Movement. The Zaman daily is also affiliated with the movement.

Istanbul Chief Public Prosecutor Hadi Salihoğlu said on Sunday that he had ordered the detention of 31 suspects on charges of forgery, fabricating evidence and forming a crime syndicate to overtake the sovereignty of the state.

President Recep Tayyip Erdoğan has vowed to take alleged Gülen Movement group members to task on numerous occasions. The government has described the movement and its supporters as the "parallel state" since late 2013.

Erdoğan said in 2012 that a bug had been found in his office and charges of political spying were brought against 13 suspects, including senior police officers.

In December 2013, an anti-graft probe targeted several high-profile figures, including the sons of three former government ministers and leading Turkish businessmen.

The government denounced the probe as a "dirty plot" constructed by the "parallel state," an alleged group of bureaucrats embedded in the country's institutions, including the judiciary and the police.

Since then, hundreds of police officers have been detained on charges of eavesdropping on Turkey's top officials, disclosing highly-sensitive information, forming and belonging to an organization designed to commit crime, violating privacy, illegally seizing personal information and forgery of official documents.