Concerns: Julie Bishop said the government had cancelled passports of Australian jihadists. Photo: Andrew Meares
Australians fighting with extremists in Iraq and Syria is ''one of the most disturbing developments'' in domestic security for some time, Foreign Affairs Minister Julie Bishop says.
Ms Bishop said the government was concerned that a number of Australians, believed to be up to 150, who were travelling through Lebanon to reach Syria were planning to move from Syria into Iraq to join Sunni militants.
On Sunday US President Barack Obama said he was ''deeply concerned'' about the threat Australian jihadists travelling to these war zones posed on their return home.
''There is no doubt the problem in Syria is one we have been paying a lot of attention to over the past couple of years as you see jihadists coming in from Europe and as far as Australia to get trained then going back into their home countries,'' Mr Obama said on CNN. ''This is something we have been deeply concerned about.''
Ms Bishop said the government had cancelled several passports of Australians seeking to fight in Iraq, as it had done when it was reported Australians were seeking to join or come back from fighting in Syria.
''We are receiving reports that they are also in Iraq where [the Islamic State in Iraq and Levant] is fighting the Iraqi security forces and so we are doing what we can across government,'' Ms Bishop told the ABC's Insiders program.
''It is a topic that is engaging the Australian government at every level.
''Our national security committee is discussing this matter and we are working out ways to ensure Australians are safe from what I find to be a deeply disturbing development in our domestic security.''
Prime Minister Tony Abbott said on Monday that the ''best thing we can do for Australians at home is to ensure that jihadis do not come back to this country''.
''I want to make it absolutely crystal clear that this is a government which believes in border security. We have demonstrated not just that we believe in border security, but we are effective in establishing border security,'' he told journalists in Melbourne.
An online recruitment video posted by ISIL featured two Australians, one of whom, Zakaryah Raad, was believed to have been killed in the fighting.
Raad was one of four men convicted of whipping a Muslim man in a punishment at a Sydney townhouse in July 2011 for drinking alcohol and taking drugs.
The video, titled ''There is No Life Without Jihad'', encourages Australians and Americans to join the fight.
It is believed to have been made some weeks ago and features Raad, using the name Abu Yahya ash Shami, and Abu Nour al-Iraqi, both of whom identify themselves as Australian.
Ms Bishop said she was in regular talks with her counterparts in Malaysia, south-east Asia, Europe and the US about the issue of foreign citizens joining the conflict.
''It's a global issue but we are particularly concerned with the reports of Australians who are heading off, not only to train, but to take leadership roles in radicalising others and, of course, the fear is that they will come back to Australia with these new-found abilities and talents in terrorism.''
But she again talked down the possibility of Australia contributing to greater military involvement in Iraq, beyond the small detachment of Australian soldiers that had been sent to guard the Australian embassy in Baghdad.
''I don't envisage that situation,'' she said. ''Certainly the Iraqi government has not requested support, has not requested Australia to provide any military support. The US has not requested us to do so.''