Two prison officers have been treated in hospital following separate incidents at the Midlands Prison today.
One officer was slashed in the back with a homemade knife and required 14 stitches after he intervened during an attack on an inmate.
A second officer was subsequently injured trying to subdue another inmate.
Two investigations by the gardaí and the Prison Service are under way following the attacks, which took place in the E wing.
In the first incident, two inmates attacked another prisoner with a shiv, or a homemade knife, but when prison officers intervened, one was slashed along the lower back.
The situation was brought under control but when senior officers subsequently came to investigate the attack, another inmate became violent.
As officers subdued him an assistant chief was kicked a number of times and suffered a broken ankle and ribs.
Both officers were taken to Portlaoise hospital for treatment.
In a statement, the Prison Officers' Association said it was deeply concerned that two colleagues had been injured in the line of duty.
POA Deputy General Secretary Jim Mitchell said: "These incidents, coming so soon after our two colleagues suffered a most serious assault at Tallaght Hospital recently, raises many issues for the Prison Officers' Association and our individual members in regard to a reasonable expectation of 'safety at work'."
The director general of the Irish Prison Service said that his thoughts are with the injured staff and their families.