As dawn broke over Sydney and Brisbane this morning, more than 800 police swarmed suburban streets, searching homes and cars in Australia’s biggest ever homegrown terrorist crackdown.

Executing search warrants across both cities, police arrested 15 people and charged one man with serious terrorism offences.

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A suspect is arrested in north-west Sydney. Photo: AAP

In Sydney’s north-western suburbs, police arrived at homes around 4am, using loudspeakers to call residents out and floodlights from a police helicopter to illuminate the area.

“I heard them calling out to him to ‘Come out!’ for about 10 to 15 minutes,” Guilford resident Mark Anderson told Sky News of a raid on his neighbour’s property.

Other Sydney suburbs targeted included Beecroft, Bella Vista, Marsfield, Merrylands, Northmead, Wentworthville, Westmead, Castle Hill, Revesby, Regents Park and Bass Hill.

According to NSW Police Deputy Commissioner, Catherine Burn, three of the 15 detainees resisted arrest forcing officers to use “reasonable force”.

One weapon, a firearm, was seized, but New South Wales police commissioner Andrew Scipione said it was too early to determine if there would be more.

In Brisbane, homes in the suburbs of Mount Gravatt East, Logan and Underwood were also raided as part of the coordinated operation.

Acting Australian Federal Police Commissioner, Andrew Colvin, said the findings of the Queensland raids, which involved 70 police officers, were not directly linked to the New South Wales operation but connections were being investigated.

“While the raids in Queensland are not directly related to what’s happened here today in NSW, the investigations continue and we are looking at linkages between the two,” Mr Colvin said.

The twin city raids have been called the largest operation of their kind in Australian history, involving extensive ground operations and officers with forensic, traffic management, tactical control and surveillance expertise.

It is believed that the group of men seized in the NSW operation were plotting to commit violent acts against members of the Australian public, a plan which Mr Scipione said had been successfully “disrupted”.

Police search at a house in Mount Gravatt, Brisbane. Photo: AAP

The raids came after reports of an incident in Sydney on Tuesday, in which two men carrying an Islamic State flag yelled anti-Christian abuse from their car outside a school in Harris Park.

Police are appealing to the public to help identify the two men, who were driving a red hatchback and were described as being of Mediterranean or Middle Eastern appearance.

Mr Scipione said today’s raids were part of an “ongoing” investigation that began earlier this year.

“The decision was made by the experts that now was the time to move,” Mr Scipione told reporters on Thursday morning.

“At this stage … we are wanting to be sure we don’t in any way compromise what we’ve got to do from this point on.”

The NSW Commissioner commended the officers involved and stressed their safety was “absolutely paramount”.

“Today’s operation reflects the reality of the threat that we actually face, but more importantly the strength and capability of our counter-terrorism forces to stop these attacks from happening,” Mr Scipione said.