Australia, a staunch ally of the United States and its battle against militants in Iraq and Syria, is on alert for attacks by radicalized Muslims.

Australian ISIS fighter Khaled Sharrouf has become the country’s first dual nationality individual to be stripped of Australian citizenship under anti-terrorism laws, the Australian newspaper said on Saturday.

Australia, a staunch ally of the United States and its battle against militants in Iraq and Syria, is on alert for attacks by radicalized Muslims, including home-grown militants returning from fighting in the Middle East.

Under a 2015 law, Australia may strip dual nationals of their citizenship if they are found to have carried out militant acts or been members of a banned organization.

Sharrouf, the son of Lebanese immigrants, shot to infamy in 2014 after photographs emerged of him and his 7-year-old son holding the severed heads of Syrian soldiers, causing a global outcry.

A spokesman for Australia’s Immigration Department told Reuters an individual had been stripped of citizenship, but declined to provide further details.