Police are investigating three overnight incidents in which a man armed with a knife stole or attempted to steal cash from businesses on Brisbane’s southside.

Preliminary investigations indicate that all three incidents may have been committed by different offenders.

Around 9.10pm last night a man armed with a knife threatened a male employee at a Wynnum Road, Wynnum West petrol station before fleeing on foot with a sum of cash.

At approximately 11.30pm a man armed with a knife stole money from a Kessels Road, Macgregor service station after threatening a female store attendant.  

A man armed with a knife attempted to rob a Kameruka Street, Calamvale convenience store around 12.45am this morning. The man threatened a male store employee and demanded cash. The employee refused, armed himself and activated an alarm causing the man to flee empty handed.

No one was injured during the three incidents.

 The man involved in the first robbery is described as Caucasian, aged in his late teens, with a slim build, wearing dark pants, dark hooded jumped, dark peak cap and had his face covered.

The man involved in the second incident is described as Caucasian, aged in his 30s to 40s with a heavy build, and wearing a black hooded top and shorts.

The man responsible for the third incident is described as Caucasian, approximately 180cms tall with a solid build. He was wearing a black balaclava, black long sleeve jumper, blue denim knee length shorts.