An elderly woman has suffered facial injuries in an attack in a supermarket car park in Oamaru.

Police are investigating after the woman, in her 70s, was knocked to the ground by an unknown male about 2.45pm on Friday, in the Countdown car park on Eden St.

Police are working to establish exactly what occurred and want to hear from anyone who may have witnessed the incident.

"We would particularly like to speak with the good Samaritan driving a red utility vehicle, who administered first aid at the scene and assisted the victim in getting home," said Sergeant Blair Wilkinson.

Anybody who can assist with information can contact Wilkinson at the Oamaru Police by emailing: [email protected].