"She was walking back through Church Street Mall on her own, when she was approached by the two men," she told reporters today.
"The males then pulled her into a garden bed, adjacent to St John's church, on Church Street Mall, where she was indecently assaulted."
The girl called out for help when a man walked past but he didn't respond, Detective Superintendent Rustja said.
"While there is no legal obligation to render assistance, certainly there is a moral one," she said.
"We would hope that members of the community that saw a girl in such distress would certainly come on board and give anyone a helping hand, or at least call the police, if they saw something like that."
But police aren't ruling out the possibility the man might not have heard her screams for help.
"He might have had ear plugs and an iPhone," Detective Superintendent Rustja said.
"He might have been under the influence of alcohol and been unsure of what he heard."
She called on the man to contact police.
"We would love to hear from you. Anything that you would have to say to us, we would be very happy to receive a phone call," she said.
Police will review CCTV footage as part of their investigation.
"We have got a substantial amount of CCTV footage and our officers are currently working on that," Detective Superintendent Rustja said.
AAP
