At least one all-girls' school has filed a police report and reached out to parents after the emergence of online advertisements asking for upskirt videos from students.

These ads on shopping apps Carousell and Locanto, believed to have been posted by the same person, offered $30 to $60 to girls in secondary schools in exchange for "upskirt fetish videos" of themselves.

The advertiser, who claimed to be a 33-year-old male, wrote that there would be more money for girls from schools with uniforms featuring pinafores, and named Paya Lebar Methodist Girls' School (PLMGS) and CHIJ Secondary as examples.

He also posted photographs of suggested poses and gave instructions on how to film the videos: "Basically flip skirt/pinafore, pull shirt from underneath and show what's under."

The ads, posted last week, were taken down earlier this week.

CHIJ Secondary principal Karen Tay told The Straits Times that the school has made a police report, as well as informed its students about the posts.

"Our girls were advised against responding to such advertisements, which prey on them, for their own protection. We have also advised them to look out for each other," she said.

"In addition, our parents have also been informed of such posts and we sought their support and partnership in emphasising the importance of not falling prey to such requests."

The Straits Times understands that PLMGS students were also advised about the posts yesterday morning.

In response to queries, a Carousell spokesman said such listing requests are rare. She added that the post was taken down on the same day it was posted, after it was flagged by other community users.

In a private chat with a concerned parent posing as an interested student, the advertiser suggested working out a long-term deal with "you and your friends if they are interested".

He also told her that the requested actions are "nothing extremely explicit. Just something you might have done before in school often".

He added that the videos are for his own use and that no faces should be shown in them. He also said he would not do meet-ups.

"This is my protection policy to you for safety and assurance," he said.

Ironically, students who respond to the user's requests for such material may be charged under the Penal Code for selling obscene videos, said criminal lawyer Sunil Sudheesan.

PLMGS parent David Chin, a 47-year-old lecturer and father of three, said he was shocked to find out that someone would be "so blatant as to put something like this on a public site".

But he has also cautioned his children, including his Secondary 2 daughter.

"We're not trying to get them overly panicked, but it is good to be aware that such people exist," he said.