NEW YORK >> The guru of a cult-like self-improvement group that attracted heiresses and Hollywood actresses was convicted today of turning his female devotees into his sex slaves through such means as shame, punishment and nude blackmail photos.

A jury in federal court in Brooklyn took less than five hours to find 58-year-old Keith Raniere guilty on all counts of sex-trafficking and coercing women into sex.

“Raniere was truly a modern-day Svengali,” Brooklyn U.S. Attorney Richard Donoghue said outside court, calling him a lying manipulator who “ruined marriages, careers, fortunes and lives.”

Raniere, a short, bespectacled figure who wore pullover sweaters in court, listened attentively but showed no reaction as he learned the verdict. His lawyer, Marc Agnifilo, said Raniere plans to appeal. He could get 15 years to life in prison at sentencing Sept. 25.

“It’s a very sad day for him,” Agnifilo said. “I think he’s not surprised, but he maintains that he didn’t mean to do anything wrong.”

Raniere once had an international following with a foothold in Hollywood with his Albany-area group, NXIVM. His adherents included actress Allison Mack of TV’s “Smallville”; an heiress to the Seagram’s liquor fortune, Clare Bronfman; and a daughter of TV star Catherine Oxenberg of “Dynasty” fame.

“This was a very frightening group,” Oxenberg said after the verdict. Her daughter India left NXIVM after her mother spoke out against it.

“I had to save a child who was caught in the grips of this cult, so I wasn’t going to stop until I succeeded,” Oxenberg said.

Prosecutors told jurors that Raniere — known to his followers as “Vanguard” and revered as “the smartest man in the world” — was actually a creepy con man who barely got passing grades in college.

A sorority made up of some NXIVM members, sometimes called “The Vow,” was created to satisfy his “desire for sex, power and control,” prosecutor Moira Penza said in closing arguments.

According to testimony, Raniere’s “slaves” were forced to give up “collateral” — nude photos and other material — to keep them in line.

Among the more damning allegations against Raniere were that he had some women branded with his initials and that he started having sex with a follower when she was 15. Prosecutors said he took nude photos of the teen that were shown, one by one, to the eight women and four men on the jury.

Raniere kept the photos stashed in his private study as “a trophy” of “his sexual conquest,” Penza said.

The defense argued that Raniere was a genuine believer in unconventional means for self-improvement and that all his sexual encounters with female followers were consensual. His behavior could be seen as “repulsive and offensive, but we don’t convict people in this country for being repulsive or offensive,” Agnifilo told the jury.

Raniere was arrested at a Mexican hideout in 2018 following an investigation into his group. Mack and Bronfman were indicted with him but pleaded guilty . Mack admitted helping Raniere assemble his harem and collect “collateral”; Bronfman confessed to committing financial crimes for him.

They didn’t testify, leaving a cooperating member of his inner circle and three victims from the secret sorority as the key witnesses.

One victim described being confined to a bedroom for more than 700 days on orders from Raniere as punishment for showing interest in another man. Another said she was blindfolded and bound to a table so that another woman could perform a sex act on her.