Port Lincoln on the Eyre Peninsula has been hit with a series of break-ins to at least 13 homes and cars on Thursday.

It has prompted an elevated police response with extra patrols being deployed in the area.

Throughout Thursday, investigators were called to nine properties around Port Lincoln where thieves had entered through unlocked doors and windows, as well as unlocked vehicles.

Police say thieves mostly stole house keys, car keys and mobile phones. In several cases, car keys were taken from homes and subsequently used to unlock cars.

About 5.45am on Thursday, a witness reported seeing a man on Highview Dr, but police have yet to identify any suspects.

Since these incidents, police have urged residents to be careful of leaving windows and doors open during the hot weather, because a cool breeze isn’t the only thing that can get in.

Meanwhile, in the northern suburbs of Adelaide, a man armed with a syringe has robbed a service station.

About 10.30pm on Thursday, a man threatened the female console operator with a syringe at a service station on Salisbury Hwy, Salisbury before leaving with cash.

The suspect remains on the run.

Anyone who witnessed this robbery, or with information about the Port Lincoln offences, is asked to contact Crime Stoppers on 1800 333 000 or online at http://www.crimestopperssa.com.au