A group of about 20 protesters blocked Old Cape road opposite the Uitenhage aerodrome on Friday by burning tyres.
Police spokesperson, Warrant Officer Gerda Swart, says they then threatened the driver of a heavy duty truck and petrol bombed the cab of the vehicle.
Damage to the truck has been put at more than R 1000 000.
Swart says a case of malicious damage to property will be opened by the Uitenhage police SAPS.
No arrests have yet been made and the road has been re-opened to traffic.