A 23-year-old man was threatened with a knife during an attempted carjacking in Rockingham this morning.
The man was driving on Ennis Avenue about 3.30am when he noticed the high beam of another car from behind.
Police say he stopped the car believing it was the police.
Two men wearing balaclavas and beanies got out of the car and tried to remove his keys from the ignition.
The victim got out of the car when one of the men opened the door before he was threatened with a small knife.
The thugs demanded his wallet and keys but later backed off and allowed him back into the car and drove off.
Police say the man was not injured but had a bag stolen.
Both men were described as about 180cm tall, with one wearing a dark green shirt and the other a red shirt.
Anyone with information on the incident should call Crime Stoppers on 1800 333 000.