Young children watching Peppa Pig and Fortnite videos on YouTube and social media have been targeted by the terrifying online "challenge" game Momo , according to primary schools in the United Kingdom.

The Momo trend, which appears to have originated in Japan, is an online viral sensation first featured on the WhatsApp social media network with an image of a sculpture of a disturbing young woman with bulging eyes, long black hair, bird legs and distorted features.

The image has been linked to multiple incidents around the world where children and teenagers have taken their own lives or attempted to injure themselves after being sent disturbing and graphic photographs.

Children who watch 'Peppa Pig' and 'Fortnite' videos online have allegedly been targeted by the terrifying viral trend 'Momo', which has been linked to the deaths of young people around the world. (Supplied)

Staff at Haslingden Primary School, in central England, yesterday claimed some of its students have begun to engage with the images.

“These video clips are appearing on many social media sites and YouTube (including Kids YouTube),” a post from the school on social media said.

“One of the videos starts innocently, like the start of a Peppa Pig episode for example, but quickly turn into an altered version with violence and offensive language.

“Another video clip is going by the name of 'Momo' which shows a warped white mask which is promoting children to do dangerous tasks without telling their parents. Examples we have noticed in school include asking the children to turn the gas on or to find and take tablets.”

Northcott School, also in the UK, mirrored the concerns on its own social media accounts by saying its own students have come into contact with the violent images linked to Momo.

A Manchester salon also shared an image of a young girl who cut her hair off after apparently viewing a Momo video.

"She is five years old and still keeps talking about Momo, her mother is absolutely devastated!" the post read.

"Thankfully we have managed to give her a cute pixie cut which she loves but still won’t promise me she won’t listen to Momo again.

"I couldn’t help but feel this monster has brainwashed her."

The Toddler Trims salon shared this image of a five-year-old girl who tried to shave her head. (Facebook)

Despite the reports, an Australian spokesperson for YouTube told 9News.com.au it would not allow Momo videos on the platform.

“Contrary to press reports, we’ve not received any recent evidence of videos showing or promoting the Momo challenge on YouTube," the spokesperson said.

"Content of this kind would be in violation of our policies and removed immediately."

According to online forums, users who engage with Momo are being “doxed” into self-harm and suicide.

Doxing occurs when someone hacks your private information and then threatens to share it online or in a public forum, akin to blackmail.

While three has been no evidence of Australian children coming into contact with the Momo trend online, eSafety Commissioner Julie Inman Grant told 9News.com.au parents still need to be wary.

"It is concerning when young people have been exposed to any content that scares them or plays on their emotions, like those reported via the Momo Challenge," she said.

Authorities have suggested the game, which has previously doxed people into hurting themselves, could be run by hackers trying to gain access to information. (Supplied)

"Unfortunately, the Momo Challenge is not the first, nor will it be the last, harmful online “challenge” or phenomenon to target our children.

"Our research shows 81 percent of parents hand their child an internet-connected device by the age of 4, so active parental engagement and oversight of a child’s online activities is critical from the start, to help ensure they are prepared for what they may encounter.

"As young people often do not have the maturity or judgement to cope with confronting content online, it’s important to guide and instil critical reasoning skills, so they are aware that not everything they see or receive online is real.

"We encourage parents to co-view, co-play, ask questions about the games and apps they are using, and let them know you are there to support them if they are upset or uncomfortable about anything they see online. "

The growing concern comes just a day after police in Northern Ireland renewed warnings about the dangerous viral sensation , saying it is threatening the lives of local children.

“Even basic open source research suggests that 'Momo' is run by hackers who are looking for personal info,” the Craigavon Police said in a statement posted to Facebook.

“Whatever or whoever is behind it, there is no disputing the content being sent is horrendous.

“The danger lies with your child feeling pressured to either follow the orders of any app via 'challenges', or peer pressure in chat rooms and the like.

“A 'curse contact' sends a number and tells you to contact them on Whatsapp. One video of such interaction… 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.”

The game has also been linked to other viral online trends such as Slenderman, which has been connected to the suicides and murders of people around the world.

The urgent calls come months after a 12-year-old girl and a 16-year-old boy were found to have taken their own lives within 48 hours of each other in Colombia, with both deaths linked to the Momo game.

A month before that, a 12-year-old girl was found dead in her backyard near Buenos Aires in Argentina, with authorities at the time also investigating potential links to the game.

The Momo sensation has been connected to similar urban horror legends as Slenderman, and has become so popular in South American countries, official warnings have been issued for parents to be aware of the dangers of the game and possible copycat accounts.

9News.com.au has contacted Google and YouTube for further comment.