An online extortionist posed as a fake modelling agent to con a vulnerable 15-year-old girl into sending him naked selfies.

Andrew O'Neill, of Dundee, then sent a topless photo of the girl to two of her friends when she became suspicious and refused to send him any more photos.

The 21-year-old tried to extort more images from her by threatening to send the pictures to her friends and family if she didn't supply him with more indecent photos.

O'Neill has been jailed for four years for the offences.

The abuse only came to light when the girl's mother was involved who called in police.

They raided his home in Baxter Park and found evidence of his online scam.

Police also discovered a massive haul of child abuse images he had amassed on a laptop, tablet and mobile phone including a picture of a five-year-old girl being raped.

O'Neill was also placed on the sex offenders register for life after he admitted the charges attempted extortion and making indecent images of children.

He was told by a sheriff that one of the images he was found with "might be described as an image of an atrocity".

Fiscal depute Nicola Gillespie told the court his victim had been contacted by O'Neill on Facebook.

He used the pseudonym "Jennifer Watts", with a profile picture showing a young, brown haired woman in her early 20s and a profile cover photo describing her as a "modelling agent".

Miss Gillespie said: "The girl has high functioning autism and can remember events very clearly.

"She received a Facebook message request from a Jennifer Watts and believing her page to be legitimate, accepted it.

"The accused complimented her on her appearance and said she had a lot of modelling potential.

"He asked her for clothed pictures. She was reluctant but he persuaded her.

"He later asked for pictures of her in her underwear and again she was reluctant but was persuaded.

"She sent images in a white lace bra and pants and he asked for more."

She added: "He then told her it was important for models to be flexible and asked if she could touch her toes and asked for pictures of her bending down touching her toes and of her looking back over her shoulder.

"He later contacted her asking if she would feel comfortable sending images fully naked.

"She was again uncomfortable but he persuaded her and she sent images from the front, back and side.

"There was no contact after that and she became suspicious.

"Around a week later he asked for more images but she said no.

"He attempted to persuade her through flattery but she was adamant."

She continued: "Following this a school friend of the complainer received a message asking if she knew the complainer followed by a topless image of her.

"The complainer said she was contacting police but the accused begged her not to and agreed to leave her alone.

"He messaged again asking if she wanted to continue modelling but she said no.

"He threatened to send the images to family and friends on Facebook if she didn't send more.

"Another friend received a message asking if she knew the complainer containing the topless photo.

"The girl's mother then became aware and contacted police."

Sheriff Alastair Brown said: "You constructed a deliberate deception in which you ensnared a vulnerable child.

"You exploited that successful deception to obtain photos of her partially undressed and ultimately obtaining naked photos.

"Having done that you moved on to blackmail and reiterated the threat by sending photos to two of her friends.

"You went on to download indecent images of children which included an image of the actual rape of a real five-year-old child.

"That is an image of the utmost depravity, indeed it might be described as an image of an atrocity."