A sexual blackmail ring that operated on the app Telegram and targeted dozens of women, including underage girls, has rocked South Korea and triggered demands for authorities to crack down on the rising number of sexual offences online.

Police on Wednesday took the unusual step of naming the man who allegedly ran an online network that lured at least 58 women and 16 girls into what authorities called “virtual enslavement” by blackmailing them into sending degrading and, in come cases, violent sexual images of themselves.

Cho Ju-bin faces charges of violating the child protection act, the privacy act and the sexual abuse act, as well as abuse, threats, and coercion, after he was identified as the blackmail ring’s leader.

The 25-year-old, who allegedly used the nickname “baksa,” or “doctor” in Korean, is accused of distributing and streaming the videos in a group chatroom on the messaging service Telegram.

Police, who have referred the case to prosecutors, made Cho’s name public after a record five million South Koreans signed multiple petitions on the presidential office website demanding that authorities reveal his identity.

“I apologise to those who were hurt by me,” Cho said as he was led out of a police station in Seoul on Wednesday, but he did not respond when asked by reporters if he had admitted to the charges. “Thank you for ending the life of a demon that I couldn’t stop.”

The decision to release Cho’s name came after the South Korean president, Moon Jae-in, denounced the crimes as “cruel”, adding that public anger was “justifiable”.

Police will also investigate users who paid up to 1.5m won (US$1,200) in cryptocurrency payments to view the abusive images allegedly uploaded by Cho.

Police said more than 260,000 people used similar sites, collectively known as Nth rooms, according to Yonhap news agency.

Cho allegedly approached women seeking part-time work and offered them payment in return for nude photographs, Yonhap said. He then allegedly threatened to reveal the women’s identities unless they sent clips of themselves performing sexual acts, including those involving violence.

Some were forced to carve the word “slave” on their bodies and pose in a way that would prove to chatroom users that they “belonged” to Cho, according to reports.

The victims included 16 girls of middle-school age, South Korean media said.

South Korea is already grappling with an epidemic of of secretly filmed images of a sexual nature, known as molka, which are then shared online.

“Through strict investigation, the police will entirely transform the social apathy to digital sex crime and strongly root out such crime from our society,” Min Gap-ryong, the commissioner general of the Korean National Police Agency, said.

The agency said 124 suspects had been arrested and 18 operators – including Cho – of chat rooms on Telegram and other social media had been detained since last September.

The Korea Herald said the Cho case proved the need to strengthen penalties for sexual crimes. Currently, those found in possession of abusive images of children receive a year in prison or a fine of 20m won – a penalty the newspaper described as a “slap on the wrist”

“To root out child sex exploitation, sentencing guidelines ought to be set from the standpoint of victims,” it said in an editorial.

Reuters contributed to this report