The 16-year-old known as Feiz left secretly in June with his friend, 17-year-old Abdullah Elmir, who had told his family he was going on a fishing trip.

When the teenagers next made contact with their families they were in Turkey and Abdullah told relatives he was going over the border. They believed he meant he was heading to Iraq or Syria.

The boys had travelled from Sydney to Perth, then Malaysia, Thailand and Turkey. It is believed both boys already had passports after travelling overseas on family holidays. It is not known who organised the trip or paid for it.

It is understood Feiz has been taken to Lebanon by his father who is planning to bring him back to Sydney soon, with the help of the Australian Federal Police.

The Attorney-General's department said the priority for the government "is the safety of this young person, and the AFP has been in regular contact with the family to ensure his safe repatriation."

A spokeswoman said that if other parents or families are concerned about family members they can contact government agencies, including the Department of Foreign Affairs and Trade or the AFP.

The spokeswoman also warned that "Australians in Syria and Iraq are finding themselves in life-threatening situations they are not prepared for. They are being kidnapped, injured and killed."

The whereabouts of Abdullah is still unknown and his family remain concerned for his welfare.They have said he is an ordinary youth who is academically bright, and liked playing X-box and hanging out with his siblings.

Sources in the community have said they do not believe Abdullah was the suicide bomber, known as Abu Bakr al-Australi, who blew himself up in a Baghdad market on Thursday, killing at least three people and injuring about 90 others.

There have been unconfirmed reports that he was also a teenager from western Sydney who left to join overseas conflicts last year.

Abu Bakr is the first Australian suicide bomber reported in Iraq. It follows a bombing last year by a man going by the name of Abu Asma al-Australi who blew himself up in an attack on an army checkpoint in northern Syria.

The bombing by Abu Bakr was welcomed by Mohamed Elomar, an Australian in Iraq, who asked that "Allah accept him".

Elomar, who is from Sydney, has been posting photos of weaponry on his Twitter account, including automatic weapons, a handgun and a grenade, and asking the question: "What would be the charge in (sic) these baby's were found in your posesion back in australia".

He has also been posting gruesome photos of war casualties.

The suicide bombing last week came as the government said it was concerned about Australians joining the fighting in the region, and reiterated that it is an offence.