A footage from a GoPro-like camera that was seized by Sydney police in relation to an anti-graffiti operation has revealed a recording of a gang rape of a 16-year-old girl.

Five men, one of them 17 years old, were arrested on Wednesday (Oct 14) in connection with the sexual assault.

The incident took place in May at a house party in the Western Sydney suburb of St. Clair, according to the New South Wales Police.

According to ABC.net, police said that up to eight men were in the room when the girl was attacked, with a number of them sexually assaulting her.

Four of the suspects, aged between 24 and 25 years old, face charges ranging from "aggravated sexual assault in company", to "filming a person engaged in a private act". The 17-year-old was also charged with resisting arrest, reported CNN.

One of them was charged with concealment of a "serious indictable offense".

The attack was not reported, but the alleged victim has since been contacted and interviewed. Police said she was undergoing counselling.

"It was quite obvious to investigators when viewing this footage that the child was either unconscious or semi-conscious during these assaults," said Detective Chief Inspector Peter Yeomans from the Child Abuse Squad.