SYDNEY (Reuters) - Australia’s counterterrorism unit was investigating the fatal stabbing of a petrol station employee, but authorities said on Friday it was unclear if the attack was related to an organized militant group.

Police said they arrested two males, aged 15 and 16, in relation to the deadly attack in the town of Queanbeyan just outside the national capital Canberra on Thursday night.

The 16-year-old was being investigated for suspected links to global militant groups, New South Wales state deputy police commissioner Catherine Burn told reporters, adding that neither youth had been charged.

“It appears at this stage that there may be links to a modus operandi that we would suggest is indicative of a terrorist attack,” Burn said without offering more details.

The crime is being investigated by the country’s joint counter-terrorism team, which includes employees of the state and federal police forces, the Australian Security Intelligence Organisation and the New South Wales organized crime investigation unit, Burn said.

Australia, a staunch ally of the United States and its action against the Islamic State militant group in Syria and Iraq, is on high alert for attacks by sympathizers of the radical group and from home-grown militants returning from fighting in the Middle East.