Gunfire has been reported during a major police incident in Auckland and two people have been taken to hospital.

Two intersections on Great South Rd in Penrose have been closed - one at Great South Rd and Church St/South Eastern Highway and another at Great South Rd and Campbell Rd - due to a police investigation, Auckland Transport said.

St John were alerted to the incident at alerted at 10.59am, a spokesman said.

One person was seriously hurt and taken to Auckland Hospital, while a second patient was taken to Middlemore with moderate injuries.

A witness, who gave her first name as Sonia, said she saw a firearm-wielding man running down Great South Road weaving in between cars, point his firearm at police officers who were chasing him. She said around three officers had guns and were pursuing him. She could hear them shouting at the man.

"He was pointing a firearm at the cops and trying to run. I could hear them shouting but my window was up and I needed to get out of there."

A truck is stopped at the intersection of Great South Rd and Church St in Penrose. (Photo / Supplied)

She said the man was running towards Greenlane and he was holding what looked like a pistol. She saw the chase unfold while pulling up to the lights at the Z petrol station on Great South Road.

She was worried the man with a firearm might run through the petrol station. She said her first thought was to "get out of there" and get home to her children. She saw a number of cars U-turn from the area to try and get away. She also reversed away from the area and travelled home on an alternative route.

A cafe manager on Church St East said his customers were sitting outside when they heard gunshots.

They didn't see the incident, the cafe manager said.

But after hearing the shots they went out onto the road to see what had happened and saw a swarm of police cars at what they thought was the site about 150m further down on Great South Rd.

Another witness says they saw a white BMW X5 with no plates speed through Ellerslie, "travelling 100km in a 50km zone."

They then saw a "large build man", who was driving the BMW hit the curb at speed, at which point the car "caught air". They saw the car's air bags deploy and the police capture the man.

A worker near the Church St intersection told the Herald she heard sirens and a number of police cars "swoop in" about half an hour ago. She also saw ambulance and a helicopter, which has since left the area.

Church St East was now blocked off and the manager said police were yet to approach his business to tell him what was happening.

She said a Linfox truck is at the centre of the cordoned off intersection, the only non-police vehicle in the area. Linfox Logistics said it was not aware one of its trucks is involved in the police incident.

Assistant Commissioner Richard Chambers will provide the latest detail on the incident, as well as more information about the fatal police shooting in Hamilton last night, at 2.15pm.

Drivers are being urged to delay their journey or use an alternative route.

Bus routes 321, 670, 743, & 295 are impacted, Auckland Transport said, and people should expect delays and cancellations.