A 26-year-old Dublin man who sexually exploited girls as young as nine through social media will be sentenced on Friday.

Matthew Horan, from St John's Crescent in Clondalkin, used Snapchat, Instagram, musical.ly and Kik to ask young girls to send him sexually explicit videos and pictures.

Warning: Graphic content

He gathered thousands of images of the girls after obtaining them through various apps.

In one case, he threatened an 11-year-old that he would circulate naked pictures of her to her friends if she refused to send him more.

He also recorded video and audio conversations with the children on Skype, including 60 videos of two nine-year-olds with whom he had contact.

The content of his conversations with many of those he contacted involved graphic descriptions of sex with children.

He was also found in possession of thousands of images of child sexual abuse involving babies, children and teens, which he repeatedly offered to circulate to others online.

At Dublin Circuit Criminal Court, Horan, who was described as "a perpetual loner" who had nothing else in his life, pleaded guilty to 11 sample charges from a total of 46.

The charges include sexual exploitation of a child and possession and distribution of child abuse images.

The court was told that gardaí seized further material during their third visit to his home last January and he may face further charges.

Prosecuting counsel Lorcan Staines took almost two hours to detail the evidence against Horan involving offences committed between 2014 and 2016.

Detective Garda David Connolly described how Horan was first tracked down after gardaí received a tip-off from a US agency dealing in child exploitation.

A username and email address linked to him was suspected of circulating images and videos of child sexual abuse.

When gardaí searched his home they seized computers, hard drives and mobile phones and found evidence of online conversations with girls in Ireland and abroad.

The court was told that six Irish girls were identified by gardaí and a further nine were not identifiable through their user names. At least some of the nine unidentified girls are believed to be in the UK and the US.

One of Horan's victims, an 11-year-old girl, was persuaded to send him naked pictures of herself.

She later wanted to cut off contact with him and said it was a mistake to have sent the pictures, but Horan threatened to circulate the pictures to her friends and followers on a number of social media sites.

The girl begged him to leave her alone, but he persisted and demanded more pictures, even after she said she would take her own life.

The parents of two nine-year-olds who were targeted by Horan described in victim impact statements their shock at being contacted by gardaí when his crimes were uncovered.

They said their children were targeted by an online predator while using phones and a tablet they had bought with their communion money to communicate with friends and watch dance videos.

The father of one of the victims said he was "completely numb" when gardaí showed him images of his daughter that Horan had in his possession.

The man said: "It felt like our home had been invaded. Watching our daughter in her bedroom and bathroom."

He also spoke of feelings of guilt that he failed to protect her and said his daughter had been confused and upset at having to make a statement to gardaí.

"It makes us sick to our stomach. We have had sleepless nights over this case," he said in a statement.

The mother of another nine-year-old victim said her daughter was nervous and upset and blamed herself, which was "unthinkable".

While these offences were being investigated, further offences were detected after the father of a ten-year-old girl found material on his iPad, which had been sent to his daughter.

He reported the matter to gardaí in Lucan who linked an email and username back to Horan.

Further searches on his electronic items uncovered thousands of images of young girls in various stages of undress.

Mr Staines said further victim impact statements from some of these girls have yet to be taken and will be handed into court before Friday.

Defence counsel Patrick Gageby submitted a psychiatric report to the court, which he said diagnosed Horan as being on the autism spectrum.

He said Horan had never held down a job and had no existence outside his internet use.

He said he had suffered greatly from the death of his mother at the age of three and had never developed socially.

Mr Gageby said while he was not blaming Horan's disorder for his reprehensible criminal conduct, it was a factor in his incessant use of the internet to access child abuse material.

Judge Martin Nolan will sentence Horan on Friday.