An investigation's been launched after a gunshot was fired at a popular bar in Auckland's CBD early this morning

The incident occurred at Dr Rudi's Rooftop Bar in the Viaduct before 3 o'clock.

Police received reports of an altercation after people who were asked to leave the bar became annoyed.

The group became aggressive, with one person pulling out a gun and firing a shot into the ceiling of the foyer.

A spokesperson says it's extremely lucky nobody was hurt - and that enquiries into the incident are already underway.

No arrests have been made yet.