Australia has deployed armed police inside parliament in the face of security threats, after foiling an alleged plot by sympathisers of the Islamic State of Iraq and the Levant (ISIL) group for "demonstration executions" in the country.

Previously, security was handled by in-house parliamentary security officers.

"There will be armed federal police in and around our national parliament at all times," Tony Abbott, the Australian prime minister, said on Friday.

"Earlier this month I was advised of chatter among these terrorist networks of a potential attack on government, government people, parliament house."

Abbott said he ordered an urgent security review in response, which recommended tighter measures at parliament in the capital Canberra.

Abbott, however, backed away from comments made earlier in the day suggesting that he himself was a specific target.

He said he was "not aware that specific individuals have been named ... but certainly government, government people, and parliament have been referred to".

Abbott said he was not concerned about his own safety.

His remarks came after hundreds of police officers staged a pre-dawn operation across Sydney and Brisbane on Thursday.

Of the 15 people detained, one has been charged with terrorism-related offences and nine released, police said. At least one gun was seized, along with a sword.

The raids came a week after Australia raised the terror threat level to "high", for the first time in a decade, on growing concern about rebels returning from fighting in Iraq and Syria.

Sydney Muslims protest

Hundreds of Muslims in the Sydney suburb of Lakemba protested against the raids on Thursday night, with speakers accusing the government of exploiting public fear in a bid to get contentious counterterrorism laws through parliament.

Abbott defended the raids against accusations of overkill.

"It was a show of strength," Abbott said. "It needed to be a show of strength. It needed to be a demonstration that we will respond with strength to any threat to our way of life and to our national security."

Andrew Colvin, federal police acting commissioner, said police conducted additional raids in Sydney on Thursday night.

"A number of people'' remained detained on Friday, Colvin said, declining to specify how many.

Counterterrorism laws allow a suspect to be held without charge for up to 14 days.

One of those detained, 22-year-old Omarjan Azari of Sydney, appeared in court on Thursday charged with conspiracy to prepare for a terrorist attack.

Another man faces a lesser weapons charge.

Mohammad Ali Baryalei, believed to be Australia's most senior ISIL member, was named as a co-conspirator in court documents. Police have issued an arrest warrant for him.