We'll stop you, PM tells young fighters

Tony Abbott has a message for anyone thinking of travelling overseas to fight in the Middle East: we will stop you.

"If you get out and try to come back we'll stop you at the border on the way back," the prime minister says.

Two brothers, aged 16 and 17, were intercepted at Sydney airport on Friday night after a luggage search raised suspicions they intended to join the conflict in the Middle East.

Mr Abbott said the arrests of the "misguided young Australians" from southwest Sydney were a sign the government's tough new foreign fighters laws were working.

"It seems they had succumbed to the lure of the death cult and they were on the verge of doing something terrible and dangerous," he told reporters on Sunday.

"I'm pleased that they've been stopped. My message to anyone who is listening to the death cult is: block your ears."