New Zealanders with luxury cars are being warned they could be targeted in a hacking scam which is sweeping Europe.

Cars including BMWs, Audis and Range Rovers are being remotely unlocked and started, using a simple hack with an easily constructed radio amplifier.

It involves altering the radio frequency in the cars, and tricking keyless sensors into thinking the owner is nearby with the key.

The scam been used in a growing number of thefts in Europe where 95 per cent of car brands now use keyless security.

An Auckland car dealer thinks it's only a matter of time before the scam gets here.

Jaguar and Range Rover dealer Alex Beacham said security technology used here is the same, so the hack could work on New Zealand cars too.

But he said New Zealand is too small for the criminals to operate easily, so any cars stolen in this way would have to be shipped out of the country.

Toyota and BMW had yet to come across the amplifier attack scam in New Zealand.

But Toyota NZ spokesman Morgan Dilks said car owners would find it difficult to guard against other than taking a few basic precautions with their vehicles.

"Owners should always know where their keys are, make sure their vehicle is always locked when unattended and is parked in a safe place," he said.

BMW New Zealand's corporate communications manager Edward Finn stressed the safety and security of customers was paramount.

"Anyone who has any concerns about the security of their car should contact their nearest authorised BMW dealer," he added.