A fantasist who used fake nude photos to blackmail schoolgirls with their faces superimposed on them has been jailed.

Sean McCuaig, of Glasgow, has been sentenced to three years in prison for targeting nine girls, between 12 and 17 years old, on social media using a string of fake names to get the youngsters to send him pictures.

He will also be supervised for a further three years.

On one occasion he posted the photoshopped picture on Facebook for her friends and family to see.

The 22-year-old, from Knightswood, Glasgow, threatened to harm the families of some of the girls if they didn't send him pictures.

He also threatened to post the pictures on Facebook if they didn't comply with his requests.

Police found a document detailing fantasies of abducting, raping and hurting one of the girls which also included thoughts of killing her.

McCuaig pleaded guilty to 20 charges spanning from January 2016 to June last year.

They include causing the girls to look at nude images with their faces superimposed on them, threatening to post and posting pictures if they didn't send sexual images.

The string of charges also includes downloading, distributing and having explicit pornographic images depicting women being raped.

McCuaig had a total of 2653 indecent images of children and 65 moving images ranging to the most serious category.

He used pseudonyms and threatened to upload naked images of females with the girls' heads photoshopped onto them.

One of the victims, a 14-year-old, contacted the Child Exploitation and Online Protection Centre to report being blackmailed in March last year.

McCauig set up a number of Facebook profiles including several in the name of Cara Smith, Cara Clark and Cara Rodgers, as well as Toby Greenhill and Philip Greenhill.

A document was also found relating to one of his victims, another 14-year-old, who was sent a picture of a nude female with her face superimposed on from someone claiming to be a girl.

The female threatened to post the fake picture online if the teenager didn't send an indecent picture, but no pictures were sent.

A 15-year-old was also sent a fake picture with her face on it, and "begged" McCuaig not to share it for fear or of being bullied.

Callous McCuaig told her to send a picture or he would post the picture and started a countdown.

She sent him a picture of her bare legs and selfies, including one of her looking upset.

The girl repeatedly begged him to stop and eventually confided in a teacher at school.

McCuaig also targeted a 12-year-old and told her to "stop telling lies" when she said the naked picture he had doctored, was not her.

He said: "If you don't admit it's you, I'm going to upload it on Facebook" before he blocked her.

The court heard family members later text her to ask about a Facebook post and she saw that McCuaig posted the picture and wrote "She's exposed now, she sends dirty nudes to everybody".

Eventually he took the image down and the account used to post it was deleted.

Sick McCuaig threatened a 14-year-old that he would do things to her family if she didn't send him pictures of herself and showed her a photo with her head photoshopped on it.

The schoolgirl sent him pictures and told him to leave her alone, but after a couple of weeks he messaged her again and claimed "I'm not done yet".

Videos of the girl were found on his computer that showed her as "hesitant, uncomfortable and awkward".