They say the girl was walking along a path between the car wash on Acacia Road and Gorse Hill when the attack happened on Saturday 28th March. The attack was reported to police on Wednesday of this week.
The suspect is described as possibly in his mid-20s, 5ft 10in or taller and slim, with brown eyes and of white or mixed race. He walked with a limp on his left side.
He was wearing a black hooded top with a face covering, black jogging bottoms with blue stripes and black Nike trainers.
Det Insp Adam Bunting said: “We know this will be a concerning incident for local residents and the wider community but I want to reassure people that we have launched a full investigation into this incident.
“We’re ensuring the victim and her family are receiving all the help and support they need.
“We have a team of skilled officers working on this case and there will be increased levels of policing activity around the area throughout today.
“I would like to speak to anyone who recognises the description of the offender, or who may have seen a man acting suspiciously in the area where the incident happened, either on Saturday March 28 or within the past few weeks.”
If you have any information or you were in the area at the time, all 101 and ask to speak to the duty sergeant at North Investigations. Alternatively call Crimestoppers anonymously on 0800 555 111.