SEOUL, South Korea — The South Korean police on Wednesday asked prosecutors to indict a 24-year-old man on charges he blackmailed dozens of young women, including at least 16 minors, into making sexually explicit video clips that he sold online through encrypted chat rooms.

The case has galvanized nationwide attention to what women’s rights advocates have called a growing problem in South Korea: a network of clandestine online chat rooms that lure young women with promises of high-paying jobs online and then exploit them sexually.

Some estimates in the local news media say that up to 300,000 paying customers use these online chat rooms, in which operators go so far as to provide tailor-made footage for individual customers that often include extremely dehumanizing sex scenes, the police say.

The man in the latest case, Cho Joo-bin, has shared such illegal video footage since late 2018 through members-only chat rooms he operated on Telegram, an encrypted messaging service popular in South Korea, the police said.