Mandurah Detectives have arrested a 23-year-old man from Greenfields after investigating a string of armed robberies allegedly committed between Monday and Thursday.
Police will allege the man entered a retail store on the corner of Pinjarra Road and Lakes Road about midday on Monday, March 27, and stole electrical items.
A staff member followed the man and requested he return and pay for the items, but the man became aggressive and threatened the staff member before riding off on a bicycle.
Police will also allege the same man went to a nearby retail store about an hour later to select numerous electronic items before leaving without paying.
A staff member approached him and he became aggressive, threatening the staff member before riding off.
It is also alleged on Thursday, March 30, the man entered a retail store he had previously attended and when staff recognised him, he threatened them with a knife.
The man has been charged with three counts of armed robbery and is due to appear before the Perth Magistrates Court on Saturday.