Police are investigating an attempted aggravated robbery at Gilles Plains.
Just before 3pm, Holden Hill patrols were called to a service station on Grand Junction Road after a man armed with a knife threatened a staff member.
Nothing was stolen and no one was physically injured.
The man is described as Caucasian, aged about 18 years, 178cm tall with a fair complexion and short cropped light brown hair. He was wearing a dark hooded top with white stripes around the shoulders and arms and a white pattern on the front along with black pants.
He left the scene on a green BMX and was last seen heading south along Wandana Avenue.