Armed police have swarmed Auckland's Grey Lynn and detained multiple men on Sussex St this afternoon.
Dramatic photographs show Armed Offenders Squad members standing over at least three handcuffed men who are on the driveway of a small villa.
Detective Sergeant Martin Friend said a search warrant was executed at the address, but did not give further details.
Police officers, who were carrying guns and wearing gas masks, left the address after about two hours. They released the men from their handcuffs and allowed them to go back into the house.
Friend said they were not charged, and enquiries were continuing.
A witness said she heard up to four large bangs that sounded like they could be gunshots.
A spokesman said the noises were distraction devices used by the Armed Offenders Squad during the initial phase of the operation.
No gunshots had been fired and no one had been injured, the spokesman said.
Forensic staff could be seen entering the property. An ambulance could also be seen at the scene but St John said it could not comment because it was a secret police operation.
One neighbour said new tenants had moved into the $1.5 million house around a month ago.
Earlier in the week, up to six patched members of the Tribesmen gang had been seen coming and going from the house. Some neighbours had laid complaints with police.
A local mum who was walking to school with her kids noticed a police vehicle at the property this morning.
A woman walking in the area about 2pm told Stuff she saw seven police cars enter Sussex St and surround a house.
"All the police got out of their cars, they stopped people from entering the street and then I heard four shots being fired."
The woman said she had also seen an ambulance at the scene.
The police activity is concentrated on a property a short walk from a police communications centre.
A neighbour said about three days ago she saw about 15 motorbikes going down the street followed by a police car. The men on the bikes were patched.