Two boys, one armed with a knife, entered a convenience store on Rundle Street and threatened staff about 2.45pm yesterday. The pair stole cash from the till and walked out.

A short time later, just after 3pm, a group of teens entered a convenience store on Waymouth Street and threatened staff.

The group stole cigarettes and money from the till before running towards Light Square. One of the teens was armed with a knife.

Police patrols swooped on the scene and arrested one of the suspects in a nearby carpark. The three other suspects were arrested in Light Square.

Two of the four arrested teens are believed to have committed the earlier robbery in Rundle Street.

A 15 year-old boy from Renown Park, a 14 year-old boy from Royal Park and a 14 year-old boy from Gawler East were all charged with aggravated robbery and have been bailed to appear in the Adelaide Youth Court on 21 October.

A 16 year-old boy of no fixed place was charged with aggravated robbery. He was refused bail and will appear in the Adelaide Youth Court today.