The gunman who killed two victims during a mass shooting in Auckland on the opening day of the Women's World Cup killed himself during a shoot-out, the New Zealand police said Monday.

The tournament's kickoff in Auckland last Thursday was overshadowed when a gunman opened fire at a building site on the city's waterfront.

A post-mortem of the 24-year-old gunman showed he was injured when shots were exchanged with armed officers, but Detective Superintendent Ross McKay said "it has also confirmed his fatal injury was self-inflicted".

Four of those injured in the shooting are still recovering in hospital, including an officer "who will have a long road to recovery", he added.