The show by San E, who performed at the Pyeongchang Olympics last year, sparked outrage when the words "I love spycam" flashed up on a screen that was part of his background set.

The 34-year-old rapper -- who has a track record of controversial remarks -- has refused to respond to the criticism, while broadcaster MBC has taken two weeks to say sorry following the January 31 broadcast.

"We apologise for having aired the concerned segment without proper filtering," MBC said in a statement Thursday.

South Korea has been fighting a growing tide of "molka", or spycam videos, which largely involve men secretly filming women in schools, offices, trains, toilets, changing rooms and on the street.

Spycam crimes reported to police surged from around 1,100 in 2010 to more than 6,500 in 2017, and many offenders share or sell photos and videos online.

According to official statistics about 98 percent of offenders are men -- ranging from school teachers and college professors to church pastors and police officers -- while more than 80 percent of victims are women.

San E, who has made a number of hit songs and has more than 460,000 followers on Instagram, is no stranger to controversy.

During a concert in December local media reported he called feminists "mentally ill" and the lyrics of one song "Feminist" read: "You say blah blah blah about South Korea's unequal gender pay...fake fact".

South Korean women make 63 percent of what men make in earnings, the highest pay gap among members of the Organisation for Economic Cooperation and Development, the Paris-based group said in a 2017 report.

Bae Bog-joo, a women's rights activist, said if the rapper was unaware of the implications of his actions, it showed his "lack of gender sensitivity" and "profound male-centred views".

"Spycam videos bring tremendous suffering to victims, not to mention they are illegal," she told AFP.

One Instagram user wrote on his page: "So you like spycam that much? Hope you get filmed then."

Smartphones sold in the South are required to make a loud shutter noise when taking pictures, but many offenders use special apps that mute the sound, or turn to high-tech spy cameras hidden inside eye glasses, lighters, watches, car keys and even neckties.

The crimes have become so prevalent that the South's female police officers inspect women's toilets in public venues including subway stations on a regular basis with special detectors for spycam videos that may be hidden inside stalls.

The rapper was not immediately reachable for comment.