They would like a man who contacted Crime Stoppers with information on August 21 to do so again.
A WA Police spokeswoman said the first victim was approached at Shell service station on Armadale Road at 12.15am.
The offenders demanded cash; one stabbed the man with a knife and they fled.
The victim sought help at a nearby home and went to hospital for a hand injury.
Soon after, the offenders approached two men walking in Matthew Stott Reserve and demanded belongings.
An offender stabbed the second victim several times, causing serious injuries, while the other assaulted the third victim with what police believe was a hammer. Both victims underwent surgery in hospital.
The offenders were described as 20-30 years, 170-180cm, fair-skinned and slim.
Police want to speak to the men pictured. Call Crime Stoppers on 1800 333 000.