Two Australian brothers aged 16 and 17 were stopped at Sydney Airport on suspicion that they were young jihadis headed to join the Islamic State group, officials said Sunday.

The young brothers from Sydney raised the suspicions of customs officials as they attempted to depart on Friday afternoon, Border Protection Minister Peter Dutton said.

He did not say where the pair were headed apart from a Middle Eastern "conflict zone." He also refused to say what was found in the boys' luggage that raised suspicion and led to the brothers beings reported to the airport's new counterterrorism unit.

"These two young men aged 16 and 17 are kids, not killers, and they shouldn't be allowed to go to a foreign land to fight then come back to our land eventually more radicalized," Dutton told reporters.

The boys' parents were "as shocked as any of us would be" to discover their sons had attempted to leave the country, Dutton said.

The boys had been radicalized over the Internet, he said. Dutton did not say who had paid the boys' air fares.

Dutton said charges would be filed against the boys, but did not elaborate. As juvenile suspects, they cannot be identified.

Governments around the world are trying to prevent youth from going to Syrian and Iraq to join the caliphate.

Australians who fight for foreign militant groups face prosecution at home. Under new laws, it became a criminal offense punishable by 10 years in prison for an Australian to enter the Islamic State-held territory without a legitimate reason.

"These were two misguided young Australians, Australian born and bred, who went to school here, grew up here, imbibed our values, and yet it seems they had succumbed to the lure of the death cult and they were on the verge of doing something terrible and dangerous," Prime Minister Tony Abbott told reporters.

"I'm pleased that they've been stopped and my message to anyone who is listening to the death cult is block your ears. Don't even begin to think you can leave" Australia, he added.

The government said last month that at least 90 Australians were fighting with and supporting terrorist groups in Iraq and Syria and have had their passports canceled. More than 20 Australians have been killed.