Warning: This article contains graphic content which may offend some people.
A terrifying new online craze in Russia is believed to have led to the deaths of several teenagers - and experts are concerned that it could soon spread to the rest of the world.
In the game, 'Blue Whale', vulnerable teens are encouraged to follow a series of challenges, culminating in taking their own lives, BBC News reports.
Participants are required to complete daily tasks for 50 days, beginning with watching horror movies and waking up at unusual hours, escalating to acts of self-mutilation.
On the final day, the manipulators behind the game reportedly instruct the youngsters to commit suicide, according to local media. The deaths of two Russian schoolgirls who fell to their death from the roof of a 14-storey apartment have been linked to the game, although these reports remain unconfirmed.
Local police said they are aware of the online "death groups", and are investigating.
Schools in the UK are concerned the craze could spread to their shores, with school principals sending out warning letters to parents. The head of Woodlands School in Basildon sent out a letter to parents urging them "to be vigilant and monitor children's internet usage", as did the principal of Chelmsford County High School for Girls, Essex Live reports.
The fears come during a time of heightened concern over youth suicide, as hit Netflix show series 13 Reasons Why has caused controversy after critics claimed it glamourises teens taking their own life.
Where to get help:
- Lifeline: 0800 543 354
- Suicide Crisis Helpline: 0508 828 865 / 0508 TAUTOKO
- Youthline: 0800 376 633 or free text 234, or email email@example.com
- Kidsline (ages 5-18): 0800 543 754