Guard punched by Brisbane food thief

A security guard has been punched in the face and threatened with a knife after challenging a woman who stole food from a Brisbane shop.

Police say the guard followed the woman out of an Inala shop after she tried to leave without paying just before 6pm on Sunday.

A man who was waiting outside threatened the guard with a knife and the woman punched the worker several times, leaving him with minor injuries. The pair fled and remain on the run.