Frightened commuters have witnessed a sickening fight on one of Melbourne's Metro trains.
The shocking fight between two men that was caught on camera by another passenger, while another passenger had to flee from the brawlers.
One of the men involved in the fight was believed to be wearing knuckle-dusters.
It's believed the fight occurred mid-afternoon on Friday, at St Albans station.
Witnesses say the attack appeared to be unprovoked and random.
Anyone with information is encouraged to call Crime Stoppers 1800 333 000 or use the Crime Stoppers online reporting page.