Police were called to Sydney's Royal Prince Alfred (RPA) Hospital on Sunday night to break up a brawl which left a nurse and two security guards injured.

The Health Services Union said nursing staff called security about 6:45pm last night after the fight erupted among about 15 family members who were visiting a patient.

Police were told a nurse who tried to stop the fight was dragged by the hair and punched several times, the union said.

It was alleged the brawl then spilled out into the hallway where two security guards who attempted to intervene were also punched.

Police confirmed they were called to the hospital and said the nurse and the security guard suffered minor injuries.

They said the brawl split off into two separate fights before officers were able to bring it under control.

The union said the riot squad was called but a police spokesman said the riot police only attended because they were in the area and the matter was dealt with by officers from Newtown Local Area Command.

The Health Services Union said the state government has failed to properly train or equip hospital security officers to deal with the increasing number of violent incidents at hospitals around New South Wales.

"Security officers within hospitals need to have the power to restrain patients, to detain patients and also the appropriate training to make sure that things can be done safely," HSU secretary Gerard Hayes said.

"It's outrageous that we need the riot squad to deal with the violence we saw last night in a geriatric ward.

"Hospital security officers are currently told they should contact police in situations like this. Clearly that response is not going to protect patients and visitors from the sort of violence that happened at RPA."

He said staff were shocked at the level of violence and visitors to the ward ran out screaming for help.

"The psychological impact of not only the staff but other visitors to the hospital, other patients to the hospital, is really important and this is where health security really needs to be taken seriously," he said.

'Everyone did absolutely the right thing'

RPA general manager Deb Willcox has defended the level of training given to staff.

"Our staff de-escalate very, very stressful situations all day in the hospital system," she said.

"This was of a scale that was unusual but it was handled absolutely by protocol, everyone did absolutely the right thing and looked after the family and the other patients and staff in the ward."

Ms Willcox said the incident was very distressing for all who witnessed it and staff were being offered counselling.

"We don't believe they were in danger. It was a very, very awful incident, no question, but I think the staff acted very quickly, very promptly and did all they could to mitigate the risk to anyone else on the ward," she said.

She said the injured nurse and security guards were treated at the hospital's emergency department and are expected to return to work in coming days.

Health Minister Jillian Skinner's office has declined to comment.

The ABC is seeking comment from the Sydney Local Area Health District.