Parents are being urged to be on the look out for a cyberbullying game called the 'Momo Challenge'.
It involves a character called Momo who targets young and vulnerable people on various social media channels.
They are then asked to perform dangerous tasks including acts of self-harm.
Gardaí and the PSNI have both issued a warning to parents.
Professor Mary Aiken from UCD's Geary Institute for Public Policy said it can start with minor challenges before escalating to more serious ones.
"It's a risk-taking, dare-based challenge where a child is targeted over a particular period of time and sent various challenges over say a 40 or 50-day period," she said.
"Effectively it can start with something relatively minor, like 'jump off a small wall' through to cutting, through to more serious acts of self-harm."