By Matt Siegel
SYDNEY (Reuters) - 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 is chatter, there has been chatter, amongst these networks, of targeting government people. There is no doubt about that," Abbott said in an interview with Australia's Channel Nine television network.
"That is why we are in the process of upgrading security at Parliament House in Canberra; that is why we are in the process of putting the Australian Federal Police in charge, not just of external security, but also of internal security in Parliament House."
In May, an Australian lawmaker caused a stir when he smuggled a fake bomb into parliament to highlight security shortfalls created by budget cuts.
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.
Up to 160 Australians have either been involved in fighting in the Middle East or actively supporting it, officials have said. 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.
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, the Sydney Morning Herald reported. He has been released on bail.
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.
(Editing by Robert Birsel)