A Sydney teenager has been arrested over an assault on a 13-year-old girl at a train station.
The teen is seen arguing with other girls before being set upon at Blacktown Station.
A group of girls punched and kicked the teen as she cowered on the ground.
She told the Blacktown Advocate "some girls came and punched me from behind".
The victim's friend tried to shield her from the attack.
The teen told the local paper she was upset that people filmed her instead of breaking it up.
A 16-year-old girl is facing charges over the incident.
The attack has prompted calls for more security at train stations.