Car owners have been reminded not to leave valuables in their vehicles after a spate of break-ins and vandalism.

Up to 25 vehicles were broken into across the inner city suburbs overnight, including at Brompton, Dudley Park, Prospect, Kent Town, Newton, Ovingham, Croydon Park and Hackney.

Several witnesses reported seeing a group of men smashing windows and denting panels with a metal pipe and machete.

One man told 7News he was woken by his car alarm just after 1am, and he scared away the suspects who were armed with machetes, crowbars and metal bars.

Police are investigating whether there are links between the attacks and are asking anyone with information to come forward.

They have advised car owners to park their car off the street in driveways or garages, or in well-lit areas.

Police say they are paying particular attention to the areas recently targeted, but are asking anyone who sees anything suspicious in or around cars, especially at night, to call the police assistance line on 131 444.