British Transport Police (BTP) officers are investigating after a woman was attacked by two teenage girls on a London-bound train at Chelmsford station.
Investigators have released a CCTV image of two girls they believe may have information about the incident, which took place around 11.20am on Sunday, 17 May.
PC Daniel Huggins, investigating, said: "The 19-year-old victim boarded the service at Colchester when she noticed two girls and three boys in their late teens, shouting loudly and using foul language that continued throughout the journey.
"As the train approached Chelmsford station and the woman rose to leave, one of the girls refused to move her legs which were stretched across the seats. As the victim stepped over them, she received a torrent of abuse from the girl and her friend who began to threaten her.
"As she made her way to the door both girls followed her and punched and kicked her, leaving her with a black eye and bruises to her face and legs."
Officers have launched a full investigation into the incident, including speaking to people in the area at the time, and viewing CCTV footage from on board the train and at the stations. They have now isolated images of two girls they want to speak to as they believe they may have information about what took place.
PC Huggins continued: "Understandably the victim was left feeling shaken by what took place. Whilst these types of incidents are rare on the rail network, when they do happen, we take them extremely seriously and will do all we can to find those responsible.
"We are eager to hear from anyone who recognises the people in the images, or was on the service and saw the incident, to come forward."
Anyone with information is asked to contact British Transport Police on 0800 40 50 40, or text 61016, quoting reference ESUB 88 of 02/06/2015. Information can also be passed anonymously to the independent charity Crimestoppers on 0800 555 111.