Armed SA teens arrested over servo hold up

Three teenagers have been charged with holding up a service station in Adelaide.

At least three boys wearing bandannas threatened a staff member with tyre irons before stealing cigarettes and the employee's wallet in a petrol station in Adelaide's west early on Tuesday, police say.

No one was injured and the suspects fled in a waiting car.

Two 15-year-olds and a 14-year-old were later charged with aggravated robbery and will appear in Port Adelaide Youth Court on Wednesday.

Police are looking for a fourth suspect.