15 people have been detained and one person charged with terrorism offences, following pre-dawn raids across Sydney and Brisbane, reports the Australian Associated Press (AAP).
Authorities confirmed at least one person had been charged and would face court in Sydney later in the day following the largest counter-terrorism in the nation's history.
More than 800 counter-terrorism police and Australian Security and Intelligence Organization (ASIO) officers swooped on homes in the early hours, with some of those detained believed to have links to the terror group Islamic State.
In Sydney alone, 25 arrest warrants were executed, reported AAP.
The joint operation comes less than a week after Australia's terror alert level was raised from medium to high.
Australian Federal Police acting commissioner Andrew Colvin said the operation which resulted in Thursday's raids began earlier this year.
"Police believe this group ... have the intention and have started to carry out planning to commit violent acts here in Australia," he said.
"Those violent acts particularly related to random acts against members of the public."
He said the operation was about police disrupting the potential for violence.
Last week, the head of the ASIO warned of the threat to the country from Islamic extremists and homegrown fighters returning from Syria and Iraq.
This issue of Islamists from Western countries joining the jihadists in the Middle East has been a problem not just for Australia.
There are also Russians, Germans, Canadians and French citizens taking part in the fighting in Syria.
As well, in February it was estimated that at least 50 U.S. citizens are fighting in Syria, and are liable to bring terrorism back to their home country once the war is over.