A gun shot and tear gas were used to control a brawl at Goulburn jail this week, which was sparked by attempts to convert inmates to Islam, according to a union official.

Key points: Corrective Services confirms prison guards shot live rounds to try to break up brawl

Corrective Services confirms prison guards shot live rounds to try to break up brawl Tear gas was used in second altercation

Tear gas was used in second altercation Union says initial fight sparked by attempts to convert inmates to Islam

New South Wales Corrective Services confirmed a live gun shot was fired during attempts to break up the fight.

The violence had been triggered by an Islamic prisoner trying to convert others within the prison, Steve McMahon, a chairman with the Prison Officers Branch of the Public Service Association said.

However, a statement from Corrective Services NSW denied the fight was religiously motivated.

The statement said the fight between two inmates started on Tuesday and when staff tried to break it up they were not immediately successful.

"When both inmates refused to cease fighting, a warning shot was fired to alert other staff of the incident, as per procedure in NSW prisons," the statement said.

Prison officers also used gas in the incident, but a second altercation occurred shortly afterwards, the statement said.

"While inmates were being led back to their cells, a fight broke out between two other inmates," according to the statement.

"Gas was again used to defuse the situation."

The statement said there were eight inmates in the prison yard at the time of the first incident and no one was injured.

'Assault rates increasing': McMahon

Mr McMahon said the fight was sparked after an inmate took issue with conversion attempts.

"These are not really peace-loving Islamic inmates," Mr McMahon said.

"We're talking about ones who have other ideas in mind and they're often some of the worst inmates that we've had to deal with for behavioural issues within the prisons."

He said the initial fight between two prisoners escalated to involve three, and then multiple other inmates joined in.

Mr McMahon, who is also a senior prison officer at Goulburn jail, said staff have been responding to a growing number of violent outbreaks within NSW jails in recent months.

"It's certainly something that has been increasing over the past 18 months," he said.

"In the six or seven months of this year, I think we've had as many shots fired as what we would've had in the previous five years.

"Our assault rates in New South Wales prisons are the highest they have been in the over 20 years that I've been working in the industry."

Last month, the State Government committed to spending $3.8 billion on 3,000 new prison beds over the next four years in a bid to deal with overcrowding.

Religious tensions could lead to more violence: union

Mr McMahon said tension over religious conversions could lead to larger-scale violence.

"With all of our jails being overcrowded, it's much clearer that we have a problem growing in the jails around conversion into Islam," he said.

"What we're sort of concerned about is not just day-to-day violence growing in the prisons on the back of this.

"We're concerned that they want to start taking this hard-line and obscure view on how to be part of society and make some statement by seriously injuring or killing a prison officer - that's a major concern for us."

Mr McMahon said a Kempsey Prison assault in April, in which a prisoner alleged carved a jihadist slogan into the head of an inmate, caused the Government to confirm there were between 60 and 80 inmates of concern across NSW.

He said more resources and training for prison officers to identify and intervene in inmate radicalisation was needed.