Police are looking for witnesses after a man performed an explicit sexual act near a young woman in Melbourne last month.
Authorities have been told the man boarded a Werribee line train at Williamstown Railway Station on February 18 at 2.30pm.
Police say he then performed a sexual act while sitting opposite a 23-year-old woman before departing at Yarraville railway station.
Transit crime investigation unit detectives have released images of a man they believe may be able to assist with their inquiries.
He is perceived to be caucasian in appearance, with a solid build, short dark brown hair and a distinctive dragon tattoo on his left ankle.
He was wearing a dark green hooded jumper, black and whitexjmtzyw shorts, grey sneakers and was carrying a grey backpack and blue beach chair.
Anyone who recognises him or with information about the incident is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report via its website.