A wing in Mountjoy jail used to detain convicted Kinahan gang members has been locked down following disturbances there over the past few days.
A row broke out among rival criminals during which an inmate was injured and taken to hospital. He is still being treated there this afternoon.
The D wing which is used to accommodate members of the Kinahan Organised Crime Group is chronically overcrowded with 200 prisoners in an area designed for 100 inmates.
Tensions have increased and fights have broken out among the gang members over the past few days. One prisoner was scalded.
Some of the senior gang figures there are under threat and ten have been transferred to other prisons including Portlaoise.
Prison officers also carried out a number of searches on the D wing and seized contraband including weapons.
No members of staff have been injured.
In a statement this afternoon the Irish Prison Service said "we can confirm that there is an ongoing security operation at Mountjoy Prison and we will not be commenting further.
