"Gun shot" noises reported during a police raid on a house in central Auckland was the sound of distraction devices, police say. 

A woman, who was walking down Great North Rd, in Grey Lynn, at around 2pm on Friday, said 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 loud bangs," she said.

A police spokesman said officers were "undertaking a pre-planned search warrant" and no shots were fired.

A Stuff reporter at the scene said four people could be seen on the ground outside a property on Sussex St, with their hands behind their backs.

Police were also inspecting three vehicles in the driveway of the house.

The spokesman later confirmed those detained had been released without charge.

"Members of the public may have heard loud noises during the initial phase of the operation  - these were distraction devices deployed by the Armed Offenders Squad.

"Police are unable to comment further at this time as the operation is still currently ongoing."

The spokesman said no-one was injured at the scene.

One resident said police had been at the address early on Friday morning as well.

Another witness said they saw 10 police cars and officers were carrying big guns.

He and a worker in a business nearby claimed to have heard gun shot noises and they saw the Eagle Helicopter at the scene.

The value of houses on Sussex St ranges from about $1.2 million to $2.2m.

The road was closed but it has since been reopened.