A 15-year-old girl was hurt after being verbally abused before being pushed and kicked in the head on a bridge in Lancaster.
Lancashire Police said the attack, believed to have been carried out by another teenage girl, appeared to be unprovoked.
The attack happened on September 2, although police only released details today, Monday.
Officers said the victim was walking along Millennium Bridge at around 8.45pm when the offender ran up behind her, shouted at her, jumped on her back and pushed her to the floor.
She then kicked and punched the victim in the head and body before running from the scene, police said.
Investigating officer PC Adam Jussub said: “Fortunately, the victim only received minor injuries but I am keen to hear from anyone who may have been in the area at the time and may have witnessed what happened to contact police.”
Anybody with any information is asked to call Lancashire Police on 101, quoting the log number LC-20130902-1453.