After their surprise retirement announcements, two K-pop stars were facing police questioning Thursday over interlocking sex scandals that have fascinated South Korea.

Live TV footage showed solo singer Jung Joon-young arriving at a Seoul police station where more than 100 journalists were waiting for him. Police say they are investigating allegations that the 29-year-old of secretly filming himself having sex with women and sharing the footage with friends in private group chats.

"I feel very sorry for causing concerns to the people and will faithfully undergo an investigation," Jung told reporters before entering the station. "I'm sorry. I'm sorry."

Jung issued a statement Wednesday saying he videotaped such footage without consent from the women in the clips and apologizing to the victims and everyone he disappointed and angered. He said he was retiring from the entertainment industry.

Jung's scandal flared while police were investigating fellow K-pop star and entrepreneur Seungri, the youngest member of the five-man group Big Bang, over an allegation that he attempted to arrange illegal sexual services for his business investors.

Seungri, whose real name is Lee Seung-hyun, appeared at the police station later Thursday, where he apologized and bowed deeply. The 28-year-old has denied the allegation, but he announced his retirement on Monday as his scandal grew.

Media reports have said Seungri was among the men in a Kakao Talk group chatroom where Jung posted his sex videos. Police said there were several Kakao Talk chatrooms involved but didn't elaborate.

The scandals have highlighted a dark side of South Korea's booming yet ultra-competitive entertainment industry. South Korean pop songs, TV dramas and films are hugely popular in Asia and beyond, but male stars have faced allegations of sexual assault and abuse and reports have been made that female entertainers and trainees are forced to provide sexual services to men in power.

Many K-pop stars are recruited by talent agencies as teenagers, some when they are elementary school students, and they often sleep, eat and train together before making a debut. Some suicides have occurred among celebrities in the industry.

Big Bang has been one of the most successful bands in K-pop since its debut in 2006, attracting huge, loyal followings in Asia and around the world. Forbes magazine reported in June 2016 that the band took home $44 million in pretax earnings in the previous year.

Seungri has been engaged in diverse business ventures, including a ramen franchise and a dance academy, and enjoyed displaying his lavish lifestyle.

Big Bang is on temporary hiatus as its four other members carry out about two years of military or alternative services, a requirement for all able-bodied men in South Korea. Seungri is set to start his mandatory military service on March 25.

By law, the ongoing police investigation cannot prevent Seungri from joining the army unless he's formally arrested before March 25 or voluntarily requests for a delay of his enlistment.

South Korea's police chief Min Gap Ryong told lawmakers Thursday that he would seek a joint investigation with military authorities if Seungri joins the army as scheduled and avoids an arrest.

Min said police would try to get to the bottom of all the allegations.

'Walking time bomb'

Industry commentators have taken aim at the business managers, notorious for demanding the strictest of training regimes and controlling every aspect of young stars' lives.

The focus on finding the winning song and dance formula came at the cost of the performers' "moral education", said entertainment commentator Ha Jae-keun, adding that many companies covered up problems until it was too late.

"If the agencies do not give sufficient care to their stars, including education and stress management, they will end up raising walking time bombs," said another industry commentator, Kim Sung-soo.

The South Korean public is demanding action and selling shares in the industry.

A petition calling on the president to crack down on predatory and corrupt practices the scandals have exposed has gathered more than 200,000 signatures.

Shares of Lee's agency, YG Entertainment, fell more than 20 percent after his sex bribery scandal was first reported on Feb. 26, while shares of other top music companies have also taken hits.

YG said Wednesday it would terminate Lee's contract at his request. A company source told Reuters the future of Big Bang as a group had not been decided.

But some fans are already walking away.

"What a scumbag. I am ashamed to say I used to be a Big Bang fan," said Jenny Eusden, an English teacher in South Korea.

"I just want people to know this is not OK."

Kaori Kuwabara, a 52-year-old Japanese fan of Big Bang said YG Entertainment should explain.

"My friends told me that I should stop being a fan of K-pop," she said as she waited outside the company's office in Seoul, hoping to put her demand for answers to company officials.