Keith Raniere, the founder of a cult-like group where women were kept on starvation diets, ordered to have sex with him and branded with his initials, has been sentenced to 120 years in prison.

It followed his conviction for sex trafficking and other crimes.

The sentence was imposed by US District Judge Nicholas Garaufis in Brooklyn, New York after a hearing where 15 former members of the Nxivm - pronounced Nexium - cult spoke out against 60-year-old Raniere.

The victims, most of whom were women, described what they called the devastating impact he had on their lives.

Raniere was also fined $1.75 million (around €1.5 million).

Earlier, federal prosecutors said they wanted the cult founder to remain behind bars for life as punishment for the "immeasurable damages" to victims he exploited as head of Nxivm, a purported self-help group headquartered near Albany, New York.

Nxivm proved a huge draw since its 2003 launch, attracting a coterie of rich and famous devotees such as 'Smallville' actress Allison Mack, and spreading into cities across the US.

But Raniere, who was arrested in Mexico in 2018, swapped the personal development training courses for sex sessions as the head of a group of up to 20 women - the youngest of whom was just 15.

Raniere has remained defiant.

In a court filing last month, his lawyers said he maintained his "complete innocence," and viewed his conviction as the result of a "media campaign involving witnesses who were motivated to testify falsely" at" an unfair trial."

Prosecutors said Raniere created a secret sorority within Nxivm called DOS, where female "slaves" turned over nude photos and other compromising materials that could be used for blackmail if they tried to leave.

Raniere was also accused by prosecutors of having a sexual relationship with a girl starting when she was 15, and who later became part of his inner circle of DOS slaves.

The girl's older sister, who was also deeply involved in Nxivm, testified at length against Raniere at the trial.

Nonetheless, the girls' father was among more than 50 people who wrote letters to Judge Garaufis urging leniency for Raniere.

Many said their lives had been greatly improved by Nxivm classes, which could cost thousands of dollars.

Followers signed up for $5,000, five-day self-help courses, but some were then financially and sexually exploited and had to follow a restrictive diet as Raniere - known as "Vanguard" - exerted his control, the jury was told during his trial.

Raniere's lawyers have maintained that no one in DOS or Nxivm was ever coerced.

Several other people affiliated with Nxivm have pleaded guilty to criminal charges, including Mack, Seagram liquor heiress Clare Bronfman as well as former Nxivm president Nancy Salzman and her daughter Lauren Salzman, who testified as the prosecution's star witness.

Clare Bronfman pictured as she attended her sentencing hearing

Bronfman, who was accused of helping bankroll Nxivm, was sentenced last month to more than six years in prison.