A gang of 20 football fans who terrorised rail passengers with sectarian chanting is being sought by police.
Passengers on the Inverness to Glasgow train were subjected to rowdy behaviour, including sectarian chanting, on Sunday, December 4.
The group jumped on seats, banged on windows and were heard singing and chanting sectarian songs.
The supporters boarded the train at Dundee shortly after 7pm, after Celtic's victory over Dundee United.
British Transport Police constable Lorraine Lowe said: "Passengers and rail staff have the right to travel without the fear of encountering anti-social behaviour of this kind.
"I am anxious to speak with anyone who travelled on this train and has information regarding the identity of those involved.
"CCTV footage from the train will also be examined as part of the investigation.The train involved was the 3.27pm service which runs from Inverness to Glasgow Queen Street via Aberdeen."
Anyone with information is asked to call British Transport Police on0800 405040 or call Crimestoppers anonymously on 0800 555111.