Police in Yellowknife are investigating an attack on a 15-year-old girl on the city's main street just after midnight on Wednesday.

The girl told police she was walking from downtown towards Old Town on Franklin Avenue at about 12:30 a.m. when a man she didn't know forced her into an alleyway between the Discovery Inn and the Legion and sexually assaulted her.

She was let go and contacted police. Police say she received medical treatment but was not seriously physically injured.

The man is described as aboriginal with longer hair. He wore dark clothing at the time and has a scar on his face. 

He may have been following the girl on the southeast side of Franklin Avenue between about 12:15 and 12:40 a.m.

Anyone with information is asked to contact Yellowknife RCMP detachment or NWT/Nunavut Crimestoppers at 1-800-222-8477 if they wish to remain anonymous.