Three of the 15 people arrested following Thursday's raids in Sydney and Brisbane were released yesterday afternoon while one man charged with firearms offences was granted bail.
That leaves Sydney man Omarjan Azari as the only suspect behind bars, charged with planning to kidnap and behead a random member of the public.
Azari, 22, is alleged to have conspired with Syria-based Australian Islamic State ringleader Mohammad Ali Baryalei to carry out the attack.
Following the raids on 25 properties on Thursday morning, two more homes in Merrylands and Menangle in Sydney's west were searched that night, but no arrests were made.
Prime Minister Tony Abbott said Thursday's raids averted a terrorist act that was likely to take place within days and that parliament had been mentioned as a possible target in chatter between terrorist networks in the Middle East and Australia.
Armed federal police officers will now take over security at Parliament House in Canberra.
Mr Abbott said police had been talking to "people of interest ... in connection with terrorist events we believe, on the basis of intelligence, were likely within a few days".
Mr Abbott said the national security challenge was more serious now than at any time in the past.
"It is a serious situation when all you need to do to carry out a terrorist attack is to have a knife, an iPhone and a victim," he said.
The prime minister said he had been advised in early September of potential threats to "government, government people and Parliament House".
This triggered a review of security and a decision to put the AFP in charge of internal and external security of the parliament.
Security is also being tightened at the venues of the weekend's football finals and at defence force bases.
Attorney-General George Brandis said Australian Muslims were "first-class citizens" and the latest threat was from criminals, not a particular religious group.
However, the Grand Mufti of Australia, Ibrahim Abu Mohammad, threatened legal action over the two-and-a-half hour detention of a senior imam at Sydney airport, while vandals spray-painted the word "Evil" across a mosque in the north Queensland town of Mareeba.
Mr Abbott rebuked the hundreds of Muslims who rallied in Lakemba, in Sydney's west, on Thursday night to protest against the raids, accusing the government of terrorising Muslims.
He said he would be very disappointed in Australians protesting in favour of IS.
"That's why I would say to those people who were noisily demonstrating ... have a good, long, hard look at yourselves."
Labor deputy leader Tanya Plibersek congratulated the Muslim community on its co-operation.
"Most of (ASIO's) good intelligence comes from members of the Muslim community who are talking about family members or associates who are engaging in behaviour that is troubling to them," she said.
Victoria's police chief Ken Lay said there were known IS supporters in his state and they were being closely monitored.
New anti-terror laws to give ASIO greater investigation powers will be debated in parliament next week.
