Police have arrested two 17-year-old girls for aggravated robbery following an incident in the CBD early this morning. 

At about 2.15am, police will allege the girls walked into a Convenience Store on King William Street and snatched two packets of cigarettes from the staff member who was behind the counter at the time. 

The girls ran away and the staff member chased them. 

When the man confronted them, one of the girls threatened him with a screwdriver. 

A scuffle broke-out and the second girl grabbed the screwdriver and tried to hit the victim inthe head.   The 28-year-old man ran back to the store and waited for police. 

He was not physically injured. 

A short time later and with the assistance of the dog patrol, the two girls were arrested in Wyatt Street. 

Both were charged with aggravated robbery and will appear in the Adelaide Youth Court later today.