A man is being treated in hospital following an incident on a train police are treating as a serious assault.
British Transport Police said their officers and paramedics attended a train in Glasgow shortly before midday on Friday.
The train was travelling between Glasgow Queen Street and Garrowhill at the time of the incident, which has prompted an appeal for witnesses.
Police are looking to identify a group of three teenagers who were on the train and departed at Bellgrove station.
They are aged between 13 and 15 and wore black face coverings and jogging bottoms, with one in a black balaclava.
Anyone with information can contact BTP by texting 61016 or calling 0800 40 50 50, quoting reference 240 of October 15.