Police have released images of a man they wish to speak to following a sexual assault on a train last week, Victoria Police say.
Investigators have been told a woman in her 50s was travelling on a city-bound Cranbourne line train shortly after 9am on Wednesday 11 October.
It is believed a man, who had boarded the train just prior to the woman, sexually assaulted her sometime between 9.05am and 9.25am.
The incident occurred as the train travelled between Carnegie and Caulfield railway stations.
The man, who is believed to be in his late 80s, is understood to have boarded the train at Oakleigh Railway Station.
Following the incident, he got off the train at Richmond Railway Station and caught another city loop train.
The man is described as about 162cm tall and unshaven with short white hair.
He was wearing a charcoal-coloured business jacket, a white and blue shirt, grey trousers and grey and white runners.
The man, who wears glasses, has a distinctive mark on his left cheek.
Detectives from Transit Crime Investigation Unit are investigating and have released images of a man who they believe may be able to assist with their enquiries.
Anyone with any information is urged to contact Crime Stoppers.