Parents are being warned of a new app which encourages youngsters to take part in dangerous challenges.
And the final challenge requires the player to commit suicide.
Blue Whale is an extremely dangerous game that is already believed to be linked to the deaths of around 130 young people, although no deaths in Britain have been linked to it.
A South Yorkshire school has this week written to parents warning them that some of their students have downloaded the app.
The letter read: "You may be aware of an app called the Blue Whale Game which has been featured in the news recently in connection with young people being challenged to carry out sinister daily challenges, the ultimate one being to commit suicide.
"No deaths in Britain have been linked to the game, but police officers have posted online warnings for parents.
"We have been made aware that some of our students have downloaded this app onto mobile phones and tablets, and would ask that you check your child's electronic equipment for any such content, delete it, and discuss the implications and risks of such apps with your child."
Participants in the game are required to take part in a 50-day challenge, set by a group administrator, which include self-harming and waking up in the middle of the night to watch horror videos.
It is believed that the game began in Russia in 2013 with young people also challenged to carve a picture of a blue whale into their arm.
The NSPCC told the Sun that children should remember 'not to follow the crowd and not feel pressured into doing anything that makes them feel unsafe'.
A spokesperson said: “Children can find it difficult to stand up to peer pressure but they must know it’s perfectly okay to refuse to take part in crazes that make them feel unsafe or scared.
“Parents should talk with their children and emphasise that they can make their own choices and discuss ways of how to say no.
“Reassuring a child that they can still be accepted even if they don’t go along with the crowd will help stop them doing something that could hurt them or make them uncomfortable.”