A marketing stunt to promote a video game sparked an armed police callout after an actor pointed a fake gun at terrified pubgoers in Auckland's Viaduct Basin.

About 20 revellers drinking outside Degree bar dived for cover after the promotions worker threatened them with a black imitation pistol about 8pm on Friday.

Witnesses said they heard someone shout "he's got a gun" and outdoor drinkers dived behind their tables.

Degree manager Steph Kurtovich said: "This guy with bandages on his hands pointed a gun at customers sitting outside. They were pretty terrified."

The stunt, to promote the release of Xbox title Splinter Cell Evolution, was condemned by police.

Senior Sergeant Ben Offner said officers could not tell the gun was made of plastic until they had taken it from the actor.

"We consider these types of stunts to be very ill-advised and have real concerns a similar one may one day end in tragedy."

Game promoters Monaco Corporation said they hired another marketing company to organise the event and had no idea that a gun would be used.

"This was by no means an attempt to get cops down there and get this sort of exposure. We do apologise, we shouldn't have had guns down there," said Duane Mutu, Monaco's marketing manager. "It was just marketing gone wrong."

Police said two men were cautioned at the scene.