A 13-year-old girl was attacked by two men yesterday while walking her dog near Mount Ainslie.

About 4pm, police were called to a horse trail at the back of Northcott Drive in Campbell, following a report of a girl being assaulted.

Police said the 13-year-old was walking along the track with her dog, having entered from Hackett, and was near the dam when she was grabbed from behind by a man.

Police say the man grabbed her around the top of her head and called for another man who was nearby to assist. As the young girl began to yell the first man grabbed her arm. The young girl continued to yell and was able to break free before running away.

A passerby found the young girl lying face down on the ground, in a disoriented state and contacted ACT Policing.

The first man is described as being about 20 years of age, very tall, with a skinny build and blonde hair, wearing white runners and a green-coloured shirt.

The second man is described as being about 20 years of age, very tall with possibly brown or blonde hair, wearing white runners and a number of earrings in one ear.

The victim was taken to The Canberra Hospital with minor injuries.

Anyone in the area about 4 pm yesterday and saw two men matching the descriptions or is able to assist police with the investigation is urged to contact Crime Stoppers on 1800 333 000, or  www.act.crimestoppers.com.au. Information can be provided anonymously.