A man getting a late-night dinner from an Auckland pizza store fought off a gunman to protect staff.

About 10pm last night a man with a sawn-off gun entered Dominos Pizza's Otahuhu branch in Atkinson Ave and repeatedly shouted "put the money in the bag", a police spokeswoman said. 

A man in the store then challenged him.

"The pair have squared off and the offender has lifted the gun above his shoulder and hit the victim, using it like a club," she said.

The man blocked the strike with his hands and the gunman then fled the store, empty handed, leaving his black backpack behind. 

Eric Lin, who was working at the store with one other staff member when the attempted robbery happened, said the brave customer noticed the gun in the offender's bag as he entered the store. 

"He was sitting waiting for his order and he's seen what he's carrying and I think, he's thought it looked like a fake gun," Lin said. 

He said he was removing money from the cash register when the customer confronted the robber.

"I was quite scared, he didn't point the gun at me, he showed it to me... I think the robber got quite shocked (by the customer)."

Lin said the store refunded the man who came to their rescue and gave him free drinks. 

The police spokeswoman said the robber collided with a rubbish bin outside the store and the sound his gun made on impact "made the victim think it was a fake".

Police dogs tracked the man to Church St, but lost his scent.

The robber is described as a Maori or Pacific Island man. 

Anyone with information about the incident is asked to contact Counties Manukau police. 

- © Fairfax NZ News