A Norwich school has joined organisations around the world in warning parents about the challenge.
The character has even reportedly cropped up on YouTube Kids, as well as WhatsApp and Fortnite streams.
There have also been claims that children have been made to undertake risky tasks - up to and including suicide - by threatening them with violence.
A disturbing image making its rounds in videos is encouraging children to self-harm and hurt other people. They are also said to be urging the kids not to tell their parents and threatening that if they do, "Momo" will go to their homes and kill them.
The Momo Challenge is a disturbing "game" that reportedly entices social media and WhatsApp users to communicate with an unknown number that sends graphic images and orders them to carry out risky and even suicidal acts.
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South Yorkshire Police have issued a warning to parents as the Momo challenge resurfaces online.
Anxious parents who have experienced it with their children are urging other parents to take caution.
What is the Momo Challenge? .
It has been linked to the death of a 12-year-old girl in Argentina and has also surfaced in countries including Colombia, India, France, Germany and the USA.
"Ensure that the devices they have access to are restricted to age-suitable content", the office wrote.
Just like any urban legend or horror story, the concept can be quite frightening and distressing for young people.Whilst this may seem obvious, it's important for you to reiterate to your child that Momo is not a real person and cannot directly harm them.
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"As a parent, it's hard to spot these videos as the harmful content doesn't appear until partway through the video".
The face of Momo originated from a sculpture by a Japanese artist.
Roman Hill Primary School, Red Oak Primary School, Elm Tree Primary Academy and Grove Primary are among the schools to have issued information via their social media channels and websites over the past 24 hours.
"A "curse contact" sends a number and tells you to contact them on Whatsapp", the statement said.
National Online Safety (nationalonlinesafety.com) which provides advice to schools, has produced a downloadable guide for parents called "What parents need to know about Momo" in response to a growing number of inquiries it says on its Facebook page it has received.
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