Australia is on high alert for attacks by radicalised Muslims or by home-grown militants returning from fighting in the Middle East, having raised its threat level to high and undertaken a series of high-profile raids in major cities.

Abbott said that some 100 Australians were fighting in Iraq and Syria backed by about 150 Australia-based "facilitators". Attorney General George Brandis said that 40 to 50 percent of those fighting overseas are believed to have dual nationality.

Security analysts have estimated that thousands of foreign fighters are in Iraq and Syria, drawn by the rise of the Islamic State radical group and travelling from scores of countries around the world.
               
Under tough new security powers won by his conservative government in October, Australian citizens can face up to a decade in prison for overseas travel to areas declared off limits.

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