“At this early stage, we are still working to confirm the exact number and nature of the injuries,” said a police spokesman.
Another woman said the incident started in Murrays Bay and moved to nearby Mairangi Bay.
“People are screaming. Everything happened so quickly. People were running, and the police were there at the same time with big guns, and they had someone in the floor at the time,” said Maria Paz Tapia.
National Police spokesman and MP Mark Mitchell said what happened near a usually peaceful beach was “tragic”. Everyone should be able to go outside “without the fear of being attacked by a knife,” he added.
He could not comment on the details of the police investigation, but said it was a “complicated crime scene” with multiple locations.
St John New Zealand said five people were injured and four of those people were taken to Auckland Hospital.
Three people have moderate injuries and two have minor injuries.
A Mairangi Bay resident said she saw “quite a bit of police” in the area.
“I saw three or four of them going by here towards Murrays Bay and also an ambulance,” he said.
Police have placed a detour around the incident and are urging people to avoid the area.