President Moon Jae-in called Monday for a thorough investigation into shocking sex crimes against women, including underage girls, in which group chat rooms of the Telegram messenger service were used.

He described the acts of the offenders in the so-called Nth room case as "cruel" behavior that destroyed the lives of victims and said he "feels sympathetic" to the "justifiable" public fury over it.

At least 74 women, including 16 minors, were sexually abused and exploited for several months, as they were virtually enslaved with threats of spreading photos of their naked bodies, according to police. They were forced to photograph or film themselves doing sexual acts, even grotesque ones. Those were shared with a host of viewers in the chat rooms. The number of members, who paid money for the materials, reportedly reaches 260,000.

Moon stressed the need to probe all members of the chat rooms, not just those who uploaded and distributed the photos and videos, according to Cheong Wa Dae spokesman Kang Min-seok.

"Police should take this incident as a serious crime and thoroughly investigate it," the president was quoted as saying.

Moon added he would like police to establish a special investigation team, if needed, for that.

He urged local law enforcement authorities to deal sternly with digital crimes against children and teenagers, in particular.

Moon also instructed his government to draw up full measures to eradicate new-type "digital sex crimes" that have continued to evolve using various platforms.

Moon's message came as a total of more than 3 million people have signed multiple online petitions, filed with his office, demanding strong punishment of offenders and asking police to make public the face and personal information of the arrested main suspect, a man in his 20s, who has been identified only by his surname, Cho. Police plan to hold a committee meeting Tuesday to decide whether to make his identity public.

On the background of the president's statement, a Cheong Wa Dae official later told reporters that Moon wants to change the "wrong perception" of criminals that they won't be caught if they hide "in anonymity."

Moon, a former human rights lawyer, regards the case as reflecting a problem linked with the social safety and basic human rights of all South Koreans, not only women, the official said. (Yonhap)