The Police Association says setting unmarked police cars on fire must be treated as an attack on the institutions of the state.
Two cars parked outside officers' homes in the Wellington suburbs of Wilton and Wadestown were torched within minutes of each other at about 2am on Thursday. One vehicle was extensively damaged.
Detective Senior Sergeant Paul Borrell of the Wellington CIB believes the cars were torched by the same person using an accelerant. He says the attacks seem to have been directed at police property, rather than individual officers.
But Police Association president Greg O'Connor says the police and the judiciary should take the attacks very seriously. It is not a good message for the public, he says, when police officers are intimidated at home.
Another unmarked police car was torched in the Wellington suburb of Thorndon in December, but police believe that incident is not connected to the latest attacks.