Police have gathered in a remote forest near the southern New South Wales town of Braidwood to mark 150 years since the worst mass murder of police officers in Australian history.

On January 9, 1867, four special constables assigned to catch the notorious Clarke Gang were ambushed and killed near Jinden, New South Wales.

Special Constables John Carroll, Patrick Kennagh, Eneas McDonnell and John Phegan were killed. Photo: Supplied/ABC

Special Constables John Carroll, Patrick Kennagh, Eneas McDonnell and John Phegan were the police killed in the exchange.

History books report that Carroll was found with a pound note pinned to his body.

The Clarke Gang was made up of relatives and friends, and known for rampaging, robbing and killing around the district.

Months after the massacre, the gang were arrested, and eventually executed for the murder.

The events happened 10 years before the Kelly Gang would become Australia’s most notorious bushrangers, and the massacre at Jinden is relatively unknown.

But Sergeant Paul Batista from NSW Police said it remained the worst mass murder in Australian policing history.

He said the incident forever changed policing nationwide.

“It nearly brought down the government. It nearly brought down the police force – the newly created police force,” he said.

Up until last year, the capture of the gang represented the largest reward offered by a single government in Australian history of £5000.

That is in comparison to the £2500 reward offered for Ned Kelly by the NSW and Victorian governments.

One of the memorials at the Braidwood Cemetery. Photo: Supplied/ABC

A large memorial for the four special constables was established at the Braidwood cemetery, but on Monday afternoon a plaque was unveiled at Duck Pond, the site of the murders.

“We’ll be reading out an official roll of honour to those four members, who paid the ultimate price,” Sergeant Batista said.

Australian Federal Police Commissioner Andrew Colvin was in attendance.

-ABC