Two prisoners have been taken to hospital following an attack in Mountjoy jail this morning.
A 29-year-old man, who is on remand, was attacked by another inmate in the A division of the prison and sustained head injuries.
A second man who came to his aid was stabbed in the abdomen.
Both men are being treated in the Mater Hospital where their injuries are said not to be life-threatening.
Gardaí have begun a criminal investigation and are examining the possibility the attack is feud-related.
The Prison Service has separated inmates from the Kinahan and Hutch criminal gangs, detaining them in different prisons.