Staff were punched and threatened at knifepoint during a 20-minute crime wave at three service stations in Adelaide’s south overnight.

Two boys and a 33-year-old man have been arrested over the hold-ups, which began about 1:30am when the teenagers allegedly entered an outlet on Marion Road at Mitchell Park.

They allegedly threatened staff and stole cigarettes, and then left.

After police arrived at the scene 10 minutes later, they were notified of another robbery at a service station at nearby St Marys on South Road.

“Two teenage boys allegedly entered the store and threatened staff before jumping the counter, punching the attendant,” police said.

They left empty-handed but moved on to a third service station on Fiveash Drive, allegedly threatening the “console operator with a knife before jumping the counter and punching him” and stealing cash and cigarettes.

A police dog was called in to assist officers as they searched the area.

Police then spotted three people inside a car at a car park on Rothesay Avenue at St Marys.

A search of the vehicle uncovered cash and cigarettes, police said.

Two 17-year-old boys from Hewett and Kilburn, and a 33-year-old man of no fixed address, were arrested and charged with three counts of aggravated robbery.

They will face court today.

During the incidents, two staff sustained minor injuries, with one requiring medical treatment.

Extracted in full form: Petrol station staff attacked during three armed robberies in Adelaide’s south – ABC News