Oamaru police are asking neighbours at Awamoa Park to be vigilant after would-be thieves broke into - and tried to start and steal - two cars at Oamaru's unofficial car sale yard at the weekend.

Sergeant Tony Woodbridge, of Oamaru, says between 10am on Saturday and 10am on Sunday two cars in the South Hill parking lot next to State Highway 1 had been entered and their ignitions tampered with.

Woodbridge says Police do patrol the area and despite being left in a visible location cars had been viewed as an easy target in the past and had been stolen or interfered with.

He advises caution to all owners trying to sell their cars at Awamoa Park.