Intelligence "chatter" has revealed that militants plan to attack Australian politicians and government buildings, the prime minister said on Friday, a day after hundreds of police carried out a sweeping counter-terrorism operation.
Prime Minister Tony Abbott said he had ordered security boosted at Parliament House in Canberra, amid mounting concerns over the possibility of attacks by Australians radicalized in Iraq or Syria.
More than 800 police were involved in the security operation in Sydney and Brisbane on Thursday, which authorities said had thwarted a plot by militants linked to the Islamic State group to behead a random member of the public.
"There are close links between Australians fighting with ISIS iin Syria and Iraq, and networks of support back here in Australia," Abbott told reporters, referring to the group otherwise known as Islamic State that has seized large stretches of territory in Syria and Iraq.
"The chatter involving Parliament House was chatter between Australians in Syria and Iraq and their supporters here in Australia."
"I'm not aware that specific individuals have been named as part of this chatter, but certainly government, government people and Parliament have been referred to as part of this chatter," he said.
U.S. Secretary of State John Kerry on Thursday called the foiled plot an "extravaganza of brutality", and said it was evidence of the radical group's ability to attack targets outside the Middle East.
Australia is concerned over the number of its citizens believed to be fighting overseas with militant groups, including a suicide bomber who killed three people in Baghdad in July and two men shown in images on social media holding the severed
heads of Syrian soldiers.
Abbott said at least 100 Australians are in the Middle East either fighting with or supporting Islamic State or other militant groups, a number that he said has been increasing in recent months.
At least 20 are believed to have returned to Australia and pose a security risk, and last week the national security agency for the first time raised its four-tier threat level to "high".
Highlighting the risk of homegrown militants returning from the Middle East, Abbott pledged on Sunday to send a 600-strong force as well as strike aircraft to join a U.S.-led coalition fighting Islamic State militants in Iraq.
Attacks could have been within days
Police said the Thursday raids were focused in western Sydney and the Queensland state capital of Brisbane, where two men were arrested on terrorism-related charges last week.
Authorities said that 15 people were detained during the operation, which involved heavily armed state and federal police officers swooping in on at least 25 properties in a highly coordinated pre-dawn raid spanning two states.
Sydney man Omarjan Azari, 22, has been charged with conspiracy to commit a terrorist act and will remain in custody until a hearing in November, authorities said.
A second 24-year-old Sydney man was charged late on Thursday with possessing ammunition without a license and unauthorized possession of a prohibited weapon. He has been released on bail.
"The advice of our police and security agencies was that attacks of this nature could take place within days," Abbott said, explaining the scope and speed of the raids.
Federal Police Acting Commissioner Andrew Colvin said that warrants continued to be issued in connection with the raids, and that police were now searching the "extraordinarily large" amount of material seized in the operation for evidence.
Both he and Abbott, however, declined to confirm how many people detained during the raids had been released, or under what legal authority they were being held if no charges had been laid against them.
"A number of people are still being detained, but I'm not in a position where I can confirm under what legislation or provisions they're being detained," Colvin told reporters.
About half of Australia's population of roughly 500,000 Muslims lives in Sydney, with the majority in the western suburbs where the raids occurred.
Several hundred people protested late on Thursday against the raids in Sydney's largely Muslim Lakemba neighborhood, where they expressed anger that the raids, and new security laws aimed at targeting extremists, were unfairly focused on Muslims.
Senator Christine Milne, the leader of the opposition Greens Party, warned about the risk of alienating and perhaps radicalizing elements of the Muslim population.
"The best way of keeping Australia safe is for the community to come together at a time like this," she said at a media conference.
"To make sure that we're not having people feeling like they're being marginalized. Like they're being rejected. Like they're being condemned because of the religion they believe in."SHOW MORE