Officers have noticed a spike in the number of thefts from cars in Shell Cove and Flinders, and are urging residents to double check their vehicles are locked.

"Car owners are being requested to take the time in the evening to go outside and physically check that they have not left any valuable portable items in the car, particularly in sight when looking into the car," Sergeant Jason Harrison said.

"Also that their car is actually locked with all windows up."

Among the most stolen items are GPS devices, laptops, mobile phones, iPads, iPods and handbags and wallets.

Taking away the opportunity to steal was a large part of preventing crime, Sgt Harrison said.

"It might seem like a hassle at the time but doing all you can in order to prevent someone from breaking into your car is worth your while," he said.

"If off-street parking if available please take advantage of this, and if you are fortunate enough to have garaging do not hesitate to park your car in there overnight."

Police have been conducting operations in Shell Cove and Flinders during the night.

Sgt Harrison urged community members to take part by ensuring they didn't become victims.

"Be alert but not alarmed," he said.

Anyone with information about thefts from motor vehicles is urged to call Lake Illawarra police on 4232 5599 or Crime Stoppers on 1800 333 000.