A 16-year-old boy will appear in a Sydney court later today charged with planning a terrorist attack on a Sydney Anzac Day event.

The NSW Joint Counter Terrorism Team arrested the teenager in his home in Auburn, in Sydney's west, yesterday afternoon.

NSW Police Commissioner Andrew Scipione said the age of the suspect was concerning.

"Now, the age of the individual is of significant concern. Sixteen years of age. A boy," NSW Police Commissioner Andrew Scipione told reporters this morning.


Mr Scipione said the boy had been charged with one count of acts in preparation or planning a terrorist act.

"Police will be alleging it was linked to the Anzac commemorations today," he said.

The arrest was the result of an investigation by Operation Vianden officers. Police believe the boy was acting alone and the threat had been "thwarted".

Officers were forced to act yesterday.

"We had to do that to ensure the safety of the community. Clearly we have taken that action with community safety on the eve of the sacred day, which is Anzac Day. I want to assure the community here in NSW that our counter-terrorism capability is such that we are able to move very quickly to prevent harm and on this occasion we have done that," Mr Scipione said.

"But the threat that was being dealt with was one that caused us to move and to move yesterday. At this stage, this particular young person has been bail refused."

Australian Federal Police Sydney commander Chris Sheehan urged people to attend Anzac Day events today.

"I want to assure the NSW community that our counter terrorism capability is such that we were able to move quickly to prevent harm," he said.

"Anzac Day should be observed by all in our community free from fear and I would encourage everyone to enjoy this special day."