A man followed three teenagers, ramming their car with his own and threatening them with a gun, after they threw eggs at his vehicle in Adelaide's north, police say.

Police patrols were called to the apparent road-rage incident on Birch Avenue at Salisbury East just after 11:30pm on Monday.

The three teenagers told police their car had been chased and rammed by another vehicle.

SA Police Senior Constable Mick Abbott said the man behind the wheel then broke the window of the teenagers' car, and threatened them with a gun.

"[He robbed] them of their mobile phones and wallets," he said.

"Fortunately there were no serious injuries."

One of the teenagers was treated at the scene for minor injuries.

Police are still looking for the man, who was driving a white Toyota Hilux ute.

"No registration of the vehicle was obtained [but] the suspect is described as wearing a red baseball cap and sort of a flannelette shirt," Senior Constable Abbott said.

The man broke the window of the teenagers' car, and threatened them with a gun. ( ABC News: Claire Campbell )

Eggs thrown at cars

Police said it was clear the incident was linked to the teenagers earlier throwing eggs at cars in the area.

"Elizabeth Police investigating the incident don't believe it's random," Senior Constable Abbott said.

"[The teenagers were] throwing eggs at cars on Main North Road just prior to the robbery.

"So that obviously escalated fairly quickly and this man took umbrage to his car being hit by eggs.

"It certainly doesn't warrant a firearm, or being rammed."

Anyone with information about the incident or the vehicle is asked to contact Crime Stoppers on 1800 333 000.