A gun was fired at an Auckland viaduct bar early today after people who were asked to leave the bar became annoyed.

Police said it was extremely lucky nobody was hurt in the 2.45am incident at Dr Rudi's Rooftop Brewing Co.

"This was an extremely serious incident with a large number of bystanders, and it is incredibly fortunate that no one was injured," Acting Detective Senior Sergeant Mark Franich said on Sunday.

The incident at Dr Rudi's happened just a fortnight after a shooting was reported at Auckland strip club Calendar Girls.

Police said a group of people who were removed from Dr Rudi's grew agitated and one presented a firearm.

"After a brief altercation with others outside of the bar, a firearm was discharged into the foyer ceiling," a police spokeswoman said.

Nobody was arrested but police were still investigating.