A teenager accused of gang-raping a 14-year-old girl with his school friends in Austria has moved to the UK, prosecutors say.

The unidentified boy is one of six youngsters apparently from migrant families who terrorised the girl at the school in Graz - Austria's second largest city - for months and reportedly raped her at least four times.

On one occasion, the schoolboys allegedly dragged their terrified victim out of the girls' toilets, stripped her naked and raped her in the canteen.

Gang-raped: Six teenage boys allegedly terrorised the girl and raped her at least four times (stock image)

The attack is said to have taken place in May last year when the girl locked herself in a toilet after being mobbed by the boys, who were aged between 15 and 16, in the playground.

To her horror, they then forced themselves inside and dragged the then 14-year-old out, it is alleged.

The traumatised schoolgirl told prosecutors she was screaming for help, and although other pupils witnessed the boys chasing her and forcing their way into the toilet, no one intervened.

The teenagers are accused of then dragging the schoolgirl into the school canteen where she was stripped naked and gang raped.

Witnesses told police the girl's screams could be heard 'throughout the whole school', and that they were stunned when teachers did nothing. And when she turned up late for class, she was reprimanded, it is claimed.

The rape was revenge for the girl dumping one of the boys, Austrian media has reported.

The school director has denied knowing anything about the attack, explaining: 'I only know about an incident in which the girl was in the class by the boys who had barricaded the door in order to keep her inside.

'The teacher managed to force the door open and helped the schoolgirl. I spoke to the school inspectorate about the incident, and then with the police.'

He added: 'I have almost 200 school kids here who are perfectly respectable, but what these boys allegedly did is simply unbelievable.'

Graz prosecutor Hansjoerg Bacher told MailOnline that all six boys are from migrant families.

Attacks: Six youngsters reportedly terrorised the girl at the school in Graz - Austria's second largest city (pictured) - and raped her at least four times (stock image)

He said the boys were being investigated for four alleged rapes - one of which is said to have happened in the school medical room.

Prosecutors are now investigating 18 people because it is suspected others, including pupils and a teacher, did nothing to stop the attack.

They are being investigated for possible charges of failing to assist in the prevention of crime.

Bacher said the female Austrian teacher had been questioned and was under suspicion of either knowing about the attack and not doing anything, or acting too late.

The girl only came forward with her story months after the alleged attacks after she moved to a new school and confided in a teacher.

All six boys were released on bail and one of them has travelled to the UK.

Bacher confirmed: 'We have not interviewed him because he is in England. We are in contact with his parents but we do not know when he will be returning.'

'We are in contact with the family defence lawyer. The boy is in England with his parents. He moved after the case became public although it is not believed that the move was connected with the allegations.