The Prison Officers' Association is seeking an urgent meeting with the Prison Service following an attack on two prison officers at Mountjoy Prison this morning.
Three prison officers were injured, with one taken to hospital for treatment.
The prison service says the situation was brought quickly under control and the prison is now functioning normally.
The officers were targeted by prisoners on the B wing landing at around 9.20am.
A group of prisoners tried to take the keys from one officer and another scuffle broke out when an officer entered a cell to carry out his duties.
When the scuffle was brought under control by other prison staff, inmates threw the contents of their chamber pots into the landings.
The POA says there is an ongoing serious problem with overcrowding in the country's largest jail.
Last night 640 prisoners were housed in the prison which has a capacity of 450, with 20 inmates sleeping on mattresses in the reception area.
The association also says the serious overcrowding problem arose following the Government's decision to close three prisons and is due to get worse with the decision to defer work on Thornton Hall by a further year.
