Yorkshire police forces have issued a warning to parents as it is claimed the Momo challenge has resurfaced online.
New! Harrogate to get six London trains daily?
North and South Yorkshire Police shared the advice on Facebook, describing Momo as a "sinister challenge".
The Momo Challenge features a disturbing image of a girl with bulging eyes and a crooked smile.
Reports of this image popping-up in the middle of child-orientated YouTube videos such as Peppa Pig have gone viral on social media.
It is then claimed the doll encourages children to add a contact on WhatsApp who then sends them violent images and dares.
A North Yorkshire Police spokeswoman said: “The best thing parents and carers can do is to make sure they know what their children are looking at online and educate them about the dangers of the internet, not just from frightening content such as this, but from real people who target them.
Harrogate lingerie shop accused of 'body shaming' after tweet goes viral
“Don’t let this distract you from the criminals that use the internet to exploit and abuse children and vulnerable people. Sex offenders, fraudsters, even bullies, pose real and significant harm, so please talk to your children and any older or vulnerable people you know and make sure they are alert to the dangers and take online safety precautions.
"We also ask people not to share disturbing content on social media, this only perpetuates the spread of it.”
Police in Rotherham said: "Momo is a sinister 'challenge' that has been around for some time. It has recently resurfaced and once again has come to the attention of schools and children across the country.
"Momo has been heavily linked with apps such as Facebook, WhatsApp, YouTube, and YouTube Kids."
However, Commons Leader Andrea Leadsom said on Thursday in Parliament that there was no confirmed evidence the so-called 'Momo challenge' genuinely poses a threat to British children.
Mrs Leadsom flagged up how charities were telling her there was "no confirmed evidence" Momo had led any children in the UK to self-harm.
She said: "We've been very clear that more needs to be done to protect young people online, including from cyber-bullying and suicide and self-harm content, and internet companies do have a responsibility to their users.
"The forthcoming online harms white paper will set out a range of legislative and non-legislative measures to keep UK users safe online.
"In the case of Momo, organisations including the Samaritans, the NSPCC and the Safer Internet Centre have said there is no confirmed evidence the Momo phenomenon is posing a threat to British children."
Here's how to safeguard your children online:
The force offered the following advice to parents from National Safety Online.
Tell them it's not real
Like any urban legend or horror story, this can frighten children. It is important to reassure your child that Momo is not a real person and cannot harm them.
Be present and talk regularly with your child
Be there when your child is online. This will give you a better understanding of what they are looking at and offer space to discuss the material. This will help your child to feel confident to come with you over distressing things they have seen online.
Device settings and parental controls
Make sure that parental controls are set up for all devices at home to help restrict what your child can see. On YouTube turn off 'autoplay' so that children can only watch what they have directly clicked on.
Regardless of how scary a trend may seems, if it's popular then children may be tempted to join in. Encourage your child to talk to you about anything they're unsure of and reiterate the importance of not succumbing to peer pressure.
Real or hoax?
Check the validity of everything you see online and be mindful things you share that aren't real may cause unnecessary worry.
Report and block
People can find ways to get around parental controls so you should always flag distressing content as well as blocking the account/ contents so your child can't view it again.
Speak to the safeguarding lead at your child's school. Make sure your child knows that if they have seen something distressing to go to trusted adults or call Childline on 0800 1111.