ACT Policing said the teenage girl was was jogging around Yerrabi Ponds, near the skate park in Gungahlin, about 4.20pm.

"The teenager was approached by a male on a black bike (possibly mountain bike) who indecently assaulted her before she pushed him away. The male offender rode off at speed in the direction of Hungry Jacks," police said in a statement on Saturday.

"The male offender is described as between 18-20 years old, tall, clean shaven with short black curly hair and tanned skin. He was wearing a black tracksuit and black Adidas shoes (with three white stripes)."