Prison officers had to break up a violent clash that erupted between Real IRA members and their former colleagues in Portlaoise Prison on New Year's Day.
It is understood that a vicious row erupted after a number of Real IRA prisoners forced their way onto the high-security facility's E4 landing and confronted a former leading member of the group last Wednesday.
The man targeted by the group is originally from Derry and is currently the commanding officer of the prisoners who have split from the Real IRA in recent months.
A spokeswoman for the Irish Prison Service last night confirmed that prison officers had been forced to intervene after a disturbance occured between inmates.
She said the row was between two inmates and that no-one was injured in the clash.
Prison sources however have insisted that up to 20 men were involved in the incident and that the Derryman received cuts to his face before prison officers were in a position to intervene.
It is understood that the row broke out just after teatime, forcing officers to lock up all prisoners for the remainder of the evening.
Sources have said that tensions remain high between the Real IRA prisoners, who have called on their army council to stand down, and their former colleagues, who insist that their campaign of violence should continue.
"There is a high degree of tension between Real IRA and ex Real IRA inmates," the sources said.
Referring to Dundalk man Liam Campbell who has been moved twice for his own safety, the sources continued: "One former Real IRA leader is not allowed on a landing because of fears for his safety. This outbreak of violence is going to further increase tension."
Campbell, suspected by security forces of being the dissident group's former director of operations, is understood to remain under threat because of his hardline stance.
"At present [Campbell] is not even allowed walk through the RIRA landing, that is how tense feelings have become," the source added.
It has been claimed that the injured Derry man, who is in charge of a landing housing former Real IRA men, non-aligned prisoners and a number of Continuity IRA members, was treated for his injuries in the prison hospital.
