Warning: This article may be distressing for some and includes references to self-harm and suicide.
Parents are concerned about reports of a new online game called the Momo Challenge which encourages children to self-harm.
The viral game uses the character Momo - a puppet-like figure with wide, deep-set eyes and a terrifying smile - to scare children into adding a contact on messaging service WhatsApp, who then hounds them with violent images and dares.
The challenge encourages them to self-harm and the ultimate post tells them to take their own lives.
One Auckland parent wrote on Facebook that her two children were very aware of who Momo was and was warning parents that the character is appearing in the middle of Fortnite videos on Youtube. Her son and his friends have been watching these videos during lunch time at school.
"Which resulted in my seven-year-old bursting out in tears shaking & telling me 'stop saying her name, now we're going to be killed!' and my five-year-old daughter jumped into my arms crying saying, 'Shes coming now'."
The video has also shown up in Peppa Pig videos.
Police in Northern Ireland believe Momo is run by hackers who are trying to harvest information.
"Whatever or whoever is behind it, there is no disputing the content being sent is horrendous," the PSNI in Craigavon wrote on Facebook.
"A 'curse contact' sends a number and tells you to contact them on WhatsApp.
"One video of such an interaction in America I've seen, shows an ominous-sounding voice recording being sent to a child telling them to take a knife to their own throat.
"Another threatens family if a 'challenge' is not completed. It's chilling viewing.
"There are numerous variations and of course now imitators."
They said the danger lay with children feeling pressured to either follow the orders on any app by carrying out "challenges", or because of peer pressure in chat rooms.
"This is merely a current, attention-grabbing example of the minefield that is online communication for kids," reads the PSNI Facebook post.
"In 2017, it was 'Blue Whale', now it's 'Momo'. There'll be something else next."
Police in the Republic of Ireland have also raised concerns about Momo, appealing to adults to supervise children and vulnerable people's online activity.
A spokesperson for the NSPCC in Northern Ireland said: "The constantly evolving digital world means a steady influx of new apps and games and can be hard for parents to keep track of.
"That's why it's important for parents to talk regularly with children about these apps and games and the potential risks they can be exposed to.
"The NSPCC publishes advice and guidance for parents on discussing online safety with their children, as well as Net Aware - the UK's only parental guide to social media and gaming apps."
Among the most common signs to watch out for include children who:
- Become very secretive, especially about what they are doing online
- Are spending a lot of time on the internet and social media
- Are switching screens on their device when approached
- Are withdrawn or angry after using the internet or sending text messages
- Have lots of new phone numbers or email addresses on their devices
It is understood the original artwork used by the hackers has been taken from a designer in Japan who has no connection whatsoever with the Momo challenge.
Where to get help:
Need to Talk? Free call or text 1737 any time to speak to a trained counsellor, for any reason.
Lifeline: 0800 543 354 or text HELP to 4357
Suicide Crisis Helpline: 0508 828 865 / 0508 TAUTOKO (24/7). This is a service for people who may be thinking about suicide, or those who are concerned about family or friends.
Depression Helpline: 0800 111 757 (24/7) or text 4202
Samaritans: 0800 726 666 (24/7)
Youthline: 0800 376 633 (24/7) or free text 234 (8am-12am), or email talk@youthline.co.nz
What's Up: online chat (3pm-10pm) or 0800 WHATSUP / 0800 9428 787 helpline (12pm-10pm weekdays, 3pm-11pm weekends)
Kidsline (ages 5-18): 0800 543 754 (24/7)
Rural Support Trust Helpline: 0800 787 254
Healthline: 0800 611 116
Rainbow Youth: (09) 376 4155
If it is an emergency and you feel like you or someone else is at risk, call 111.
-RNZ / BBC