A 54-year-old man was left with facial injuries after being attacked on board a train as it travelled between Edinburgh and Fife.
The incident happened on the Dundee-bound ScotRail service on Saturday between 11.15pm and midnight.
Officers at British Transport Police received multiple reports about an “aggressive” man on board.
The attack is thought to have happened between Edinburgh and Kinghorn.
Police issue description of train suspect
A British Transport Police spokesperson said: “The suspect is described as white, 6ft tall, in his late 30s to early 40s, and had bleached blonde hair. He was also wearing an orange t-shirt.
“Officers are appealing for anyone who witnessed what happened to come forward and assist their investigation.
“If you witnessed the incident or have any further information, please contact BTP by texting 61016 with reference 754 of September 24.”
