An off-duty police officer was punched twice after having his ear licked by a fellow passenger on a train between Aber and Llanbradach.
The 26-year-old man was assaulted as he travelled home from work on Saturday August 22 on the 10.35pm train from Cardiff Central to Rhymney.
Detective Constable Dilwyn Lewis, who is investigating the incident, said: “Shortly after the train left Aber railway station, a man, who was part of a larger group, approached the victim and licked his ear.
“When challenged over his behaviour, the man became aggressive and abusive towards the victim, and threatened him with violence.
“The victim then identified himself as a police officer and produced his warrant card, before telling the man that, due to his behaviour, he would be ejected from the train at the next stop.
“Another member of the group intervened and the victim was again threatened. The service then arrived at Llanbradach and, as the victim went to remove the group from the train, he was punched to the face.
“While subsequently attempting to arrest one of the men, the victim was physically obstructed by another member of the group and was again punched, this time to the jaw. The men then made off from the station.”
British Transport Police have released CCTV images of three men they would like to speak to in connection with the incident.
DC Lewis added: “We now need to speak to the men pictured, as we believe they may have key information that could greatly assist our investigation.
“I am calling on anyone who recognises them – or who has any information about the incident – to please get in touch.”
Anyone with information can contact British Transport Police on 0800 40 50 40 quoting reference WSUB/B2 of 15/10/2015.