An eight-year-old girl has been targeted by a predator posing as Justin Bieber.

The nightmare of most 21st century parents became a reality for Alicia Bellette this week, when her little girl was approached by an online predator asking for nude photographs.

A predator posing as Justin Bieber.

The mother, from Melbourne’s western suburbs, said she was apprehensive about allowing her eight-year-old daughter Charli to download the popular app Musical.ly on Saturday, reports The Age.

Her little girl had never used social media before, so Bellette took care to ensure the account was as private and secure as possible.

Yet within just 48 hours, notifications flashed up on their iPad. A fellow user of the app – which is used by children to create and share music videos – had sent several messages to the Charli under the name ‘The Real Justin Bieber’.

The schoolgirl opened them in front of her mother.

"Who wants to win a five minute video call with me?" the first message read, according to The Age.

Then, "All you need to do is send me a photo of you naked, or of your vagina."

"Lots of girls send me these pics all the time I will never tell anyone."

And finally, "message me right now if you want to do it".

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Bellette said she was instantly sickened by what she'd read, and immediately blocked and reported the user to app administrators.

She then took the iPad to a local police station. But, while officers were reportedly "horrified" by the messages and promised to look into it, they warned her it would be unlikely they'd have any success in locating the offender among the app's 130 million worldwide users.

"For her to only have seven friends, and for him to be able to find her on such a private account, it worries me sick," Ballet told The Age.

"I'm thankful I was standing over her that day and I'm hoping she would have made the correct decision, but at the end of the day she's eight years old."

As cyber safety expert Susan McLean told The Project on Wednesday night, there's no safe way for children to use the Musical.ly app, or indeed most like it.

"Yes, you can have a private account, yes, you can turn location services off, but that doesn't stop any of your followers taking your content and re-sharing it," she said.

For her, the key is to educate parents and school communities about such dangers, and for them to then share that knowledge.

"Because the alternative," she said, "is when we have a large proportion of children pestering Mum or Dad to have apps they shouldn't have, and the parent gives in because it seems the majority are allowing it."