Police say thieves are targeting cars in several areas of Bristol to steal items left on view.
The Longwell Green, Kingswood, Bradley Stoke, Stoke Gifford, Severnside and Hanham areas had been especially targeted, a police spokesman said.
Inspector Angus Krouwel added: "Thieves are causing a lot of damage to vehicles by smashing windows or forcing doors.
"They are also taking satellite navigation systems, handbags, laptop computers and cash."
Motorists have been warned to remove items from view and ensure valuables were not left in vehicles.