An 18-year-old man who raped and sexually assaulted two children, one of whom has Down Syndrome, has been jailed for six years.

The Central Criminal Court heard that in August 2014 he admitted to twice raping and once threatening to kill his first victim - an 11-year-old boy - but later went on to rape a teenage girl who has Down Syndrome.

The man pleaded guilty to four counts of rape, one count of threatening to kill and one count of sexual assault between June 2013 and December 2014.

Mr Justice Patrick McCarthy said the offences were "of the utmost gravity" when committed on children, especially one with a disability.

He also noted the man had threatened to kill one of the children to prevent him reporting the crime.

The first victim has speech and language and developmental difficulties.

His mother was made aware of the rape when her son's friend told her in July 2014.

The attack occurred when the boys were playing in a field and their ball went into a ditch.

The accused man raped the boy and did not speak to him during the attack.

However he threatened to kill him if he told anyone.

In a victim impact statement the woman told the court she noticed a change in behaviour in her son from 2013 when he started taking extra showers and excessively washing himself.

He later told her he had been raped.

The mother said a permanent scar had been left on her son and he was now undergoing treatment and lashes out.

She said he was not the son she remembers from a few years ago.

"He was ten years of age when he was first raped and 11 when he was raped for the second time. I feel he will never recover from this. I feel helpless and guilty and that I should have noticed something was wrong with him the previous year," the mother stated in a victim impact report stated

The accused man voluntarily went to a garda station on 18 August 2014 with his mother where he made full admissions to raping the boy on two occasions.

The second victim was a girl with Down Syndrome.

On April 5 2015 her mother was helping her shower when she heard her daughter say the accused had kissed her.

Prosecuting counsel told the court the teenager has said the accused man had put his tongue in her mouth and she did not like it.

 The accused knew the victim for a while and he told her she was his boyfriend so she would not tell anyone.

The court heard he knew she had special needs.

In their victim impact statement the girl's parents said their daughter's "loving nature" had been "snapped away from her" by a person who knew her circumstances, disability and routine.

"He knew what he was doing and the damage he would do. She is self-harming now a lot and has a total distrust of the male sex. Our hearts have been ripped apart."

Defence counsel Brendan Grehan SC, said his client was 15 years old when he began offending. He has no previous convictions and has since attempted to take his own life as a result of his shame and disgust.

His parents disowned him when he made full admissions.

Counsel told the court he was instructed to apologise unreservedly to the court for his client's behaviour.

The court heard that medical personnel who had treated him described him as being naïve and of an immature disposition.

Counsel said that while he is doing well in jail there are concerns about the process that is in place for when he ultimately leaves prison.

Justice McCarthy sentenced the defendant to three years for the offences on each victim to run consecutively and ordered he undergoes five years post-release supervision and undertake sexual offenders therapeutic courses.