Three police cars have been destroyed in a brazen attack after a mystery man poured petrol on them and set them alight.

The cars were parked on Leake Street behind Fremantle Police Station in Western Australia, where they were set on fire just after 11pm overnight.

Terrified tourists watched from the balcony as the fires broke out.

Police are now hunting a man who was seen at a petrol station earlier in the evening.

Footage shows him arriving on the scene holding a jerry can.

"If this person is watching right now, I would encourage this person to surrender to police," Commander Greg Knott said.

"We will find you, it's only a matter of time."

Although the Fremantle police fleet is now down three cars, they say operations won't be affected.

A review of security at the station is now underway.

Anybody with information is urged to contact Crime Stoppers on 1800 333 000.

Source: 9News