British Transport Police (BTP) officers are appealing for witnesses after a 17-year-old girl was assaulted on board a train in Birmingham.

The victim boarded the 15.43 Birmingham New Street to Redditch service on December 17 alongside a group of three teenage girls who sat next to her.

Shortly after the train departed Birmingham New Street, the teenage girls began asking the victim for cigarettes and made comments about her trainers.

One of the girls then grabbed the victim by her neck and pulled her to the floor before punching her in the face and stomach.

The three girls left the service at Selly Oak rail station and the victim realised that her black Samsung mobile phone, worth about £100, was missing following the assault.

Despite a search of the Selly Oak area, police were unable to locate the teenage girls suspected of carrying out the attack.

The suspects are all described as white and aged between 16 and 18.

One is described as being of stocky build with dark brown hair in a ponytail. She wore large silver-coloured earrings, a black jacket and tracksuit bottoms.

The second was of skinny build with dark brown hair and was had lots of make up on her face. She was wearing a black Adidas track suit with gold trim.

The third had ginger or blonde-coloured hair.

PC Linsi Robinson said: “This was a very nasty, unprovoked attack on a young passenger who was left very shaken by the incident.

“We believe the train was very busy at the time of the attack and we would urge anyone who witnessed what happened, or who thinks they may know the identities of those involved, to please come forward and contact British Transport Police immediately.”

Anyone with information is asked to contact BTP on 0800 40 50 40, quoting log reference 407 of 17/12/2009.