Adnan Oktar, the larger-than-life head of a cult accused of criminal activities, is set to appear for the first hearing of his trial along with alleged members of his criminal organization.

The trial of 226 defendants, including 167 jailed in pre-trial detention and those at large, will be held in a courtroom in Istanbul's Silivri district. A 3,908-page indictment awaits defendants while 125 plaintiffs are also expected to attend the hearing.

Oktar is known as a flamboyant televangelist who surrounded himself with surgically enhanced women in his hours-long shows on a now-defunct TV channel his followers ran.

The indictment portrays him and his followers as a dangerous cult which exploited gullible recruits and built a criminal empire thriving on blackmail and other wrongdoings. Oktar was arrested last year, along with dozens of his followers and aides, in a criminal investigation that saw police raids at the mansion where he lived and TV studios where his show was broadcast.

His depiction in the indictment is far from eccentric personality seen on TV spouting conspiracy theories and anti-evolution discourse. Prosecutors say the gang he led was involved in a recruitment scheme since the late 1990s and this involved brainwashing young women.

"The organization used its good-looking members to deceive young girls and women. Those members raped or sexually abused women and were blackmailed first by members pretending that their affairs were recorded on video. They were brainwashed under the pretext of religious teachings," prosecutors say in the indictment.

More serious charges against Oktar's organization include attempted political and military espionage, torture, abduction, money laundering, illegal wiretapping, fraud, threats, attempted murder and forgery. Oktar himself faces up to 871 years in prison for similar charges and for aiding the Gülenist Terror Group (FETÖ), sexual abuse of minors, sexual assault, blackmail and abduction. Espionage charges likely refer to his close relations with Israel, media outlets reported earlier.

Oktar was a household name in the 2000s but his prominence dates back to the 1980s when he was arrested for "promoting theocracy" for his views. He resurfaced in 1999 when he was charged with blackmail although he was found mentally ill by a court and spent months in a psychiatric hospital before his release. He made a comeback with a series of anti-evolution books and launched a TV station in 2011.