A 14-year-old boy has been put on the Sex Offenders’ Register after subjecting vulnerable schoolgirls to terrifying online abuse.

The Carlisle teenager – just 13 when he committed the offences – used social media websites such as Facebook to bully the girls into sending him intimate photos and videos of themselves.

One was just 11-years-old.

Another was so traumatised she tried to kill herself.

Carlisle’s magistrates court heard the disturbing details of the case as the schoolboy sat impassively in the dock, his distraught mother sat beside him, crying silently.

The boy, who cannot be named for legal reasons, admitted six offences of inciting girls aged between 11 and 14 to engage in sexual activity.

After hearing the details, District Judge Gerald Chalk sentenced the boy to 18 months detention and training, saying he found his offences so disturbing that he had to lock him up.

Pamela Fee, prosecuting, said the boy’s offending followed a repeated pattern as he used social media to befriend his unsuspecting victims.

The boy began targeting the girls after he was given a mobile phone for Christmas by his grandfather, his mum said. He then began spending a lot of time in his bedroom.

First he sent messages asking to go out with the girls and declaring he loved them, and then he asked for pictures of them in their underwear.

Once he had them, he threatened each girl, demanding increasingly intimate and sexual photos and videos – saying otherwise he would post photos on social media and send them to his friends.

The boy even asked one 13-year-old to get her pre-school age brother to sexually abuse her in a video.

Faced with his repeated threats to post the earlier pictures, the girls felt they had little choice but to give in, said Mrs Fee.

“He also threatened to get the girls battered if they contacted the police,” she said.

Mrs Fee read detailed impact statements from the girls, most aged 13.

One wrote: “I couldn’t take it any more and got a kitchen knife and threatened to kill myself with it. I don’t want to be here any more. My mum got the knife off me but I can’t control my emotions.”

Mrs Fee said that in June 2015, despite being cautioned by the police, the boy continued contacting victims and making sexual demands.

Mark Shepherd, defending, conceded a background Probation Service report concluded the boy was at a high risk of reoffending.

But he said: “His mother would welcome any assistance from the Youth Offending Service to stop this. Her heart broke when she heard the nature of the messages [sent by her son].”

Judge Chalk told the boy he had no alternative but to lock him up.

“This is a truly exceptional case when I have to send someone of your age to custody,” he said.

“It’s clear you have caused significant psychological harm... I also find it very disturbing that these offences occurred while you were subject to a conditional caution.”

The boy’s name will be on the Sex Offenders Register for five years. He will also be subject to a Sexual Offences Prevention Order severely restricting his access to the internet.