Parents are being warned to monitor children's social media use after an online challenge has circulated.

The 'Momo Challenge” involves online trolls being disguised as a 'Momo”, an evil looking character told to have supernatural powers to possess and kill children.

Stuff reports says that the Momo contacts children through social media apps such as WhatsApp and instructs them to self-harm or suicide.

The Momo threatens children, claiming to harm the child or their family if they don't do what is instructed.

YouTube have issued a statement on Facebook in regard to the social media challenge.

'We've seen no recent evidence of videos promoting the 'Momo Challenge” on YouTube. Videos encouraging harmful and dangerous challenges are against our policies.

'If you see videos promoting harmful or dangerous challenges on YouTube, we encourage you to flag them to us immediately.”

Parents are encouraged to keep an eye on their children's social media habits to ensure their safety online.