New Zealand Police are warning parents about the dangers of a sick social media ''game'' that's said to be responsible for hundreds of teenage suicides in Russia.
The "Blue Whale challenge" encourages at-risk participants to take part in a series of tasks like cutting themselves every day for 50 days.
They are then instructed to kill themselves on the final day of the sick "challenge".
Waikato District Police took to Facebook to warn those about the harmful smartphone app.
"We have received a couple reports of a new smartphone app called Blue Whale.
"Without getting into the nitty-gritty, the app is particularly nasty as it targets young people and encourages them to complete self-harm challenges and eventually suicide.
"It has apparently been a bit of an issue overseas.
"I have a had a quick look in the Apple App Store this morning and can't seem to find it, which is a good thing. In saying that though, if it does somehow seem to find it onto your young person's phone we would recommend deleting it straight away."
Police said it's a timely reminder to monitor what your children are looking at on their phones.
The panic about the online challenge was prompted by the death of two teenagers in Russia last month who were believed to be participating.
Two schoolgirls Yulia Konstantinova, 15, and Veronika Volkova, 16, fell to their deaths from the roof of an apartment block in industrial Ust-Ilimsk.
Another girl named only as Ekaterina, 15, was critically injured after she fell onto snowy ground from a flat in the city of Krasnoyarsk, also in Siberia.
Just two days earlier a 14-year-old girl from Chita, near Mongolia, was reported to have thrown herself under a commuter train.
In all cases state investigators are probing whether a controversial web ''suicide game'' has influenced the girls to seek to take their lives.
Yulia left a note saying ''End'' on her social page and earlier she had posted a picture with a big blue whale, seen as a symbol of the social media movement encouraging children to take their own lives.
Her friend Veronika wrote: ''Sense is lost ... End.''
She regularly posted sad messages such as ''Do you feel that gradually you become useless?'' or ''I'm just a ghost''.
It was reported that two teenage boys were detained by police at the scene after allegedly filming the tragic double suicide.
As part of the "game", teenagers were urged to use a knife or razor to make the shape of a whale on their wrist or leg, say Russian reports.
They were also urged to watch horror movies all day, and to wake themselves at 4.20am, in steps leading up to demands to take their own lives on the 50th day of the "game".
There was deep concern last year when there were fears that the sinister masterminds behind the online challenge could be behind at least 130 suicides across Russia.
After the arrest of a supposed ringleader, there was a reduction in cases, but now there are new fears of vulnerable teenagers being swayed by the game.
Investigative newspaper Novaya Gazeta reported last year: "We have counted 130 suicides of children that took place between November 2015 to April 2016.
"Almost all these children were members of the same internet groups and lived in good, happy families."
It went on: "We know absolutely for sure that adults are working with children, with the help of knowledge of their habits and passions, using their favourite language and culture.
"They know psychology well, they convince girls that they are 'fat', tell boys that they are 'losers' in this world. And that there is another world and they will be among the chosen."
A report on Ren TV said that an internal report by the FSB secret service, once headed by Vladimir Putin, "indicated that the problem of provoking suicides among underage children via the internet is really serious".
Last year an alleged ringleader named as 21-year-old Philip Budeikin was detained and charged with organising eight groups between 2013 and 2016 which "promote suicide".
Some 15 teenagers committed suicide, and another five were rescued at the last moment, according to the case against him.
Children were told via such social media that "the best things in life start with the letter 'S' - semiya [family], Saturday, sex, suicide."
A song tells them: "We have left for the open space, we have nothing left in this world."
The children are asked: "How many dull days like this are you going to drag yourself through?"
A picture of an approaching train has a sign: "This world is not for us."
A photograph of teens on a roof is captioned: "We are children of the dead generation."
Where to get help:
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• Samaritans 0800 726 666
• If it is an emergency and you feel like you or someone else is at risk, call 111.
- With Daily Mail