A prisoner is in hospital fighting for his life after an attack at Mountjoy Prison, Dublin.
ardaí investigates the aggravated assault that took place on Friday evening.
The man, who is in his thirties, is currently being treated for serious injuries at Mater Misericordiae University Hospital.
He was sentenced last week to six and a half years for possession of a semi-automatic pistol.
A Garda spokesperson said the scene has been technically investigated and an emergency room has been set up at Mountjoy Garda station while the investigation is ongoing.
It is understood that four men entered the man’s cell and subjected him to aggravated assault.
Prison officers arrived on the scene.
A number of prison officials are also required to testify to gardaí.
CCTV footage is said to be available of the four men entering the victim’s cell.
The Irish Prison Service has confirmed that a prisoner was seriously injured in an incident.
“The matter is under investigation by the Prison Service and also subject to investigation by Garda,” it added.