The sister of an Irish teenager who has spent a year in jail in Egypt after he was arrested during a siege at a mosque has said her brother has been severely beaten in prison.

Ibrahim Halawa was detained with three of his sisters when they were caught up in the Al-Fath mosque siege in Cairo. The three women were allowed home to Dublin last November, but their 18-year-old brother remains in prison.

It was revealed at the weekend that Mr Halawa began a hunger strike on Wednesday after a mass trial involving over 400 defendants was abandoned. It is understood the presiding judge has referred the case to another court, although no hearing date has been set.

Ibrahim's sister Nosayba Halawa visited her brother yesterday and says he has been badly beaten. Speaking to Newstalk Breakfast earlier, she described the situation:

Amnesty International has concluded that Mr Halawa is a prisoner of conscience, detained solely for peacefully exercising his right to freedom of expression.

The organisation says Mr Halawa was shot in his hand when the security forces stormed the building, but was not given access to medical care for his injury, and the only treatment he received was from a cellmate who happened to be a doctor.

He was held in detention with adults contrary to Egypt's Child Law, which provides that children must be held in juvenile detention centres and be separated from adults.