A large police presence descended on the park for the planned operation just before 1pm on Wednesday, with live aerial vision showing police searching a vehicle in the middle of the road.

Police had been following the men throughout the day and chose Centennial Park for the arrest because it was the "earliest opportunity and safest location".

A 27-year-old Constitution Hill man, a 34-year-old Crows Nest man, and a 39-year-old man from The Ponds were taken to Waverley Police Station on Wednesday. Each of the men were charged with two counts of possessing an unauthorised pistol, possessing ammunition without holding a licence, knowingly dealing with proceeds of crime and participating in a criminal group.

They were refused bail to appear at Waverley Local Court on Thursday.

"We received information about these three gentlemen which caused us to arrest those people today," Detective Acting Superintendent Damien Beaufils said.

"Again, they were armed with firearms and it was fairly important that we arrest them today."

Photos posted to social media showed what appeared to be bullet holes in the front windscreen of a white van. But police have confirmed no shots were fired during the arrests.

Detective Superintendent Beaufils said the noise heard by park users came from a tactical device known as a non-lethal projectile, which was used to "subdue the men".

He said police had no suspicions about where the men were going, rather they received information that they were in possession of firearms, "and so the decision was made to arrest them and seize the firearms".

Both guns seized in the operation were semi-automatic; a Beretta and a Smith & Wesson.

The arrests, part of Strike Force Mangowa, are connected to "an ongoing investigation by the State Crime Command organised crime squad".

Police said that the operation was not related to counter-terrorism.

Aerial footage shot by Seven News showed police searching a white four-wheel-drive with its doors flung open parked in the middle of Grand Drive. Officers could be seen photographing objects on the ground.

The footage shows police seizing several items, which were examined on the side of the road.

According to the ABC, witnesses saw police officers wearing balaclavas searching a vehicle, while others reported hearing loud bangs.

The operation occurred about 100 metres from the park's main cafe.

Centennial Park is bordered by several affluent suburbs and is a popular park for exercising and sporting events.

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