An "active shooter" is on the run in Sydney after one person and multiple cars were hit by a gunman. The incident at Croydon Park started on Sunday evening, when a shooter is said to have opened fire from a roof unleashing four rounds. Local reports suggest at least one person was shot.

A New South Wales (NSW) Ambulance spokesperson told NewsWire that a man in his fifties had arrived at Canterbury Hospital with a gunshot wound and has since been transported to another site. Three others reportedly presented themselves to Campsie police station with minor injuries, two of whom were taken to hospital, while another was treated at Croydon Park before also being hospitalised.

Police have swarmed the area in inner-western Sydney and put it under lockdown, with residents urged to "stay inside".

Helicopters have also been seen circling around Croydon Park and Campsie.

Reports on the ground suggest the shooter was on the roof of a restaurant when gunfire was heard at around 7:30pm local time. 

A spokesperson for New South Wales (NSW) Police said: "A police operation is currently underway at Croydon Park after shots were fired."

"The area has been locked down with Georges River Road closed between Croydon Avenue and Seymour Street and Brighton Avenue closed between Georges River Road and Queensborough Road," they added.

"Specialist resources are attending, the public is urged to stay inside and motorists are advised to avoid the area. Further information will be provided when available."

Sources also told local media that cars including a NSW police vehicle were shot at while attempting to respond to the incident.