A statement given by a witness, who was a former member of Gülenist Terror Group (FETÖ), included in an indictment against the group shows its members kept sex tapes of high-profile businessmen in order to blackmail them and extort money.

FETÖ, who is being blamed for the failed coup attempt that left 248 people dead on July 15, 2016 and a string of other wrongdoings, face criminal charges in the northwestern province of Bursa.

Eighty defendants, including 36 who are still being sought by police, stand accused of running a terrorist group. Prosecutors are asking for three instances of aggravated life imprisonment for the defendants, which include the group's U.S.-based leader Fetullah Gülen.

A secret witness, who testified to prosecutors, said that FETÖ used Bank Asya, run by its supporters, to preserve sex tapes belonging to 11 businessmen in the city known for its large textile and machinery production sector.

Along with secretly recorded tapes, documents showing annual revenues of businessmen were kept in a secret safe in a local Bank Asya branch. The witness said the practice was not limited to businessmen and the group had lists of every bureaucrat and low-ranking civil servants loyal to FETÖ kept in a Bank Asya safe.

Prosecutors are investigating what happened to the tapes and documents after the witness said that a FETÖ member visited the bank and fled with the safe's content just hours before police raided it for its links to the terrorist group.

The FETÖ member, who donned a wool hat and scarf to conceal his face from security cameras, was identified as İ.S.S., a member of the group known to authorities.

The witness said it was unlikely that the terrorist group destroyed the tapes and documents.

A businessman, who testified to prosecutors, said FETÖ's infiltrators in local tax department had access to private financial information of businessmen and companies and relayed them to point man Cansun Sarıyıldız, who was FETÖ's so-called Bursa "imam."

The witness also said that Sarıyıldız and Şahabettin Harput (a former Bursa governor detained for ties to the terrorist group) would visit those businessmen and ask for "donations" in the name of the terrorist group.

This is not the first time FETÖ has been accused of using sex tapes for blackmail.

A few months ago Çetin Acar, who was a senior figure in the group before he severed his ties a few years ago, said in a trial that the group even hired female followers and sex workers to blackmail and extort people, from ministers to generals, by secretly recording their sexual affairs.

Acar had claimed that the group had employed some 3,000 prostitutes, as well as female followers of the terrorist group and members of the cult, and sent them to top military brass, ministers, lawmakers and other figures to secretly videotape affairs in order to blackmail the victims later.

He claimed some generals, arrested for their involvement in the July 15 coup attempt that is being blamed on a small Gülenist junta, might have been blackmailed to join the group because of this.

Acar said FETÖ formed a gang especially to handle blackmail by sex cases, and Cihangir Çelik, the former head of the Turkish police's anti-terror unit, led the gang.

FETÖ was able to orchestrate these sex tape scandals thanks to its infiltrators within law enforcement. A former police chief and 37 others were arrested in August 2016 for planting hidden cameras.

Deniz Baykal, chairman of the main opposition Republican People's Party (CHP) resigned in 2010 after sex tape recordings from hidden cameras emerged showing him with his former secretary and deputy.

The same year in 2011, several lawmakers from the opposition Nationalist Movement Party (MHP) stepped down after hidden camera sex tapes showing their extra-marital affairs were leaked online. Meanwhile, Faruk Bayındır, a prominent businessman who leaked the sex tapes, remains at large after a court issued an arrest warrant for him on charges of being member of FETÖ.