Casey Crime Investigation Unit detectives are investigating an armed robbery and assault in Hallam early this morning.
Investigators have been told three men walked from Hallam Train Station towards the Hallam Valley Trail about 1.30am.
The men were then approached by three unknown males.
The offending three men asked the victims for a lighter before one of the victims was assaulted.
They then produced weapons before making demands for a mobile phone.
The three victims, two 18-year-old men from Hampton Park and a 19-year-old man from Berwick were taken to hospital in a stable condition.
The three offending men are described as Islander in appearance and were all wearing dark clothing.
Police would like to speak to anyone who saw the group of men around Hallam Train Station about midnight or who may have witnessed the incident.
Anyone who witnessed the incidents or with information is urged to contact Crime Stoppers on 1800 333 000 or make a confidential on-line report at www.crimestoppers.com.au