A Member Loyal To The Islamic State In Iraq And The Levant (ISIL) Waves An ISIL Flag In Raqqa.
A member loyal to the Islamic State in Iraq and the Levant (ISIL) waves an ISIL flag in Raqqa June 29, 2014. REUTERS/Stringer

Australian teens Abdullah Elmir, 17, and a 16-year-old boy are believed to have crossed the border to fight with the ISIS in Iraq, AAP reports.

Elmir left their home in Sydney on June 20 to go fishing. However, he then called her mother after a week, saying he was in Turkey and was about to "cross the border", Zali Burrows, lawyer for the family told press Monday. Elmir's mother could not fathom how these minors were able to leave the country without any interference from authorities.

''The family went to the media today as a plea to the government to bring their boy back. We know they have the intelligence to pinpoint him. The concern is that he's being used as a tracking device to gather further intelligence, to see where he's actually going to go, '' Ms Burrows said.

The family has never met the 16-year-old boy that Elmir was believed to be travelling with.

The tandem is believed to have taken the indirect route from Sydney to Perth, then to Malaysia and Thailand, and thereby reaching Turkey.

On Thursday, Foreign Minister Julie Bishop confirmed that there are 150 Australians who are now fighting with the militants in Iraq and Syria.

Bishop said that several passports were already cancelled following advice from intelligence agencies to prevent these Australians for travelling back to the country as they pose terrible security risk.

"In Syria it seems that over a period of time they have moved from supporting the more moderate opposition groups to the extreme, and that includes this brutal extremist group ISIS. We are concerned that Australians are working with them, being radicalised, learning the terrorist trade and if they come back to Australia of course it poses a threat." Bishop told ABC's AM program.