A court has reportedly heard a 25-year-old man 'encouraged' the gang-rape of a 16-year-old girl as it was filmed on a GoPro camera.

Three of the five men accused of gang-raping the teenager in Sydney's west will remain behind bars until their next court date.

Four men aged in their 20s and a 17-year-old boy have been charged of the multiple assaults that allegedly took place in St Clair in May.

They were charged after police found footage of the attack on a GoPro camera seized as part of an investigation into graffiti.

Penrith Local Court heard Tristan Carlyle-Watson 'encouraged' the other men as the alleged act was filmed, Fairfax Media reported.

Tristan Carlyle-Watson (pictured) has been charged with concealing a serious indictable offence. A court heard he 'encouraged' other men as the alleged gang rape was filmed

Mr Carlyle-Watson, 25, was charged with concealing a serious indictable offence over the incident and was formally refused bail after not applying

Four men and a teenage boy have been charged over the gang rape of a 16-year-old girl at a Sydney party

Mr Carlyle-Watson, 25, was charged with concealing a serious indictable offence over the incident and was formally refused bail after not applying.

In remarks on Thursday, Detective Chief Inspector Peter Yeomans from the Child Abuse Squad said his officers were 'horrified at what they saw in the footage.

''It's horrible. It's terrible what happened to this young girl.'

Police alleged up to eight men were in the room at the time of the assault.

When brought before Penrith Local Court, Kurt Stevenson, 24, who faces three charges of aggravated sexual assault in company, did not apply for bail.

It was formally refused and he will remain in custody until he appears before the same court on December 10.

One of his co-accused, 23-year-old Andrew Waters, has been charged with aggravated sexual assault in company and aggravated indecent assault in company.

Waters didn't apply for bail and has been ordered to reappear before Penrith Local Court on the same day as Stevenson. He is due to return to Penrith Local Court on December 11.

Police said footage of the incident back in May was uncovered on a GoPro camera that was later seized

Another man, 24, is set to front court later on Thursday. The 17-year-old's case is set to be heard on Thursday as well.

The victim was either unconscious or semi-conscious at the time and the attack was not reported, but officers had since contacted and interviewed her, Det Chief Insp Yeomans said.