The two constables, both aged 25, serving in Sydney’s south-west were leaving a concert in Newtown when they came across a group having a “heated” discussion on Enmore Road around 11pm.

One officer was left unconscious after being punched and repeatedly kicked in the head and witnesses helped perform CPR before paramedics arrived.

He remains at Royal Prince Alfred hospital in a serious condition.

The second officer suffered facial injuries and has since been released from hospital.

NSW Police Superintendent Despa Fitzgerald said police were now hunting three persons of interest after the assault.

“I’m confident, we have positive lines of inquiries,” Fitzgerald told media today.

“We will be hunting down those persons of interest, we will be knocking on your door, so if you have anything you want to say, please hand yourselves in to police.”

Fitzgerald thanked the witnesses who rendered CPR on the seriously injured officer and said “anything could have happened” if they weren’t there to help.

She said police were looking for any CCTV, dashcam or phone footage of the “violent, confronting and distressing” incident.

Police have not yet spoken to either officers and Fitzgerald said some details remained murky.

NSW Police Minister Yasmin Catley thanked the witnesses, including an off-duty nurse, who came to the officers’ assistance.

“We have such gratitude for you coming in and helping those officers, particularly that officer with crucial injuries,” Catley said.

“The police [officers] themselves are thankful.”

She added: “Get these perpetrators and to get them behind bars. This is a dangerous attack and we do not want them on our streets.”

Police say the two officers were walking along Enmore Road when they approached three men unknown to them who were having an argument.

“The two off-duty officers were assaulted with one of them knocked to the ground and repeatedly punched and kicked to the head,” NSW Police said in a statement.

“The second man, also aged 25, suffered facial injuries and was also taken to hospital for treatment; however, has since been released.”

The three men behind the attack fled the scene before police arrived and detectives are calling for help to find them.

A crime scene has been established and police are investigating under Strike Force Rabnor.

One of the men is described as being of Maori or Pacific Islander appearance, aged between 20 and 30, with short black curly hair, a white t-shirt and dark blue jeans.

The second man is described as having Caucasian appearance, in the same age bracket and wearing a tan vest, tan cargo pants and black sneakers.

The third man, also described as being of Maori or Pacific Islander appearance and aged between 20 and 30, has long brown curly hair, a long sleeve black flannelette shirt, grey trackpants and black slides.

Anyone with information is urged to contact police or Crime Stoppers.