Four arrests over Sydney cash truck heists

Four men have been arrested in Sydney after they allegedly pulled off brazen daylight robberies of armoured cash trucks during three separate heists in as many months.

The group is believed to be behind robberies of cash-in-transit security guards in Marrickville in early May and Double Bay and Alexandria in July.

They armed themselves with pistols, revolvers, crow bars and "long objects" to threaten the guards, police said, but on the second occasion fled empty-handed.

The group used two stolen cars - an Audi S3 and a Renault Megane - during their robberies.

Police arrested the men at Cremorne, on Sydney's north shore, on Monday afternoon and said they were caught driving a stolen car.

Two of the men attempted to run away and one was allegedly in possession of a revolver.

They were taken to North Sydney police station for questioning.