Australian authorities foiled what they believed to be a large-scale terrorist attack, arresting 15 people during raids in Sydney and Melbourne.
"I am satisfied that we have disrupted what I would regard as the final stages of a large-scale terrorist attack, or the launch of a large-scale terrorist attack here in Australia," New South Wales Police Commissioner Ken Moroney told ABC radio.
The arrests come less than a week after Prime Minster John Howard said Australia received intelligence about a "terrorist threat".
Australia, a staunch US ally with troops in Iraq and Afghanistan, has never suffered a major peacetime attack on home soil.
The country has been on medium security alert since shortly after the September 11th, 2001, attacks on the United States.
Mr Moroney said more than 400 officers were involved in the overnight raids of 15 homes in Sydney's southwest, resulting in the arrest of six men.
"They are currently being interviewed by police and my expectation is that those persons variously will appear in Sydney courts this morning."
Nine other arrests were made in Melbourne, the ABC reported.
Australia's parliament rushed through urgent amendments to anti-terror laws last Thursday to allow police to charge people in the early stages of planning an attack.