Teenage girl attacks woman who 'stopped them picking on young children' on packed commuter train

Disturbing footage has emerged of a group of teenage girls attacking a young woman and allegedly robbing her of her phone.



The video - from NBC Philadelphia - shows a scrum of bodies as about ten girls appear to assault a lone woman on a busy train carriage .



A witness told the local NBC station that the victim had stepped in earlier to defend a different set of girls from the attackers.



They then turned on her, with one of the assailants repeatedly punching her in front of horrified commuters.



One passenger captures the entire ordeal on her mobile phone , and although the attackers seem aware they are being filmed they continue their assault.



One member of the group then appears to snatch the woman's phone as she shouts "My phone!"



The gang of girls then get off the train at Philadelphia's City Hall, leaving their scared victim nursing head and facial injuries.



The attack happened on a Southeastern Pennsylvania Transportation Authority train on Tuesday afternoon.



The service is a commuter train in Philadelphia, the sixth-largest U.S. city, with more than 100,000 people using it every day.



A police investigation into the brawl is underway.