Fairfax Media understands that the group of Australian Defence Force personnel will primarily liaise with the US military, which recently sent about 250 of its troops to guard its embassy in the city.

If the Australian embassy experiences an immediate threat, its staff would likely be moved to the much larger US compound for safety.

A spokesman for Defence Minister David Johnston said that a ''small Australian Defence Force liaison element has been deployed to the Australian embassy in Baghdad to support security arrangements''.

As Fairfax Media reported earlier this week, Australia's elite SAS soldiers could be sent to Baghdad to evacuate diplomats if the security situation in the Iraqi capital deteriorates sharply.

The last Australian troops pulled out of Iraq barely six months ago after the eight-year US-led war.

Australia withdrew most of its forces in mid-2008, when then prime minister Kevin Rudd declared "mission over".

But 11 Australian military officers continued to serve with the United Nations Assistance Mission in Iraq (UNAMI) in a deployment known as Operation Riverbank until November last year.

Prime Minister Tony Abbott said on Friday that the government's first priority was ''ensuring that our people in Baghdad are safe and that we have the capacity to remove them if necessary, to move them safely if necessary''.

He also reiterated warnings that up to 100 Australians were in Syria, Iraq and the surrounding region fighting with Islamic extremist groups and may try to come home.
He branded them ''murderous potential terrorists coming to this country''.

Mr Abbott vowed the government would either prevent them from returning to Australia or lock them up if they returned.

''We are keeping as careful a watch on all of these individuals as we possibly can,'' he said.

''Be in no doubt: some individuals from this country are now participating in acts of barbarity in Iraq.

''These people should have no place in our country and we will do our best to keep them out and if they can't be kept out, they will be taken into detention because we are not going to allow people who are an obvious threat to our safety and security to roam loose in Australia.''

There have been calls to consider revoking the citizenship of Australians who go to fight with extremists in the Middle East, but this is considered legally difficult and Immigration Scott Morrison branded such a move ''a very extreme measure'' on Thursday.

But it is a crime under Australian law to fight with such a group as the Islamic State of Iraq and the Levant, and therefore returning Australian jihadists could be prosecuted.

The latest developments follow an announcement by US President Barack Obama that the US would send up to 300 ''military advisers'' to bolster the Iraqi government's efforts against insurgents from an al-Qaeda splinter group who have swept through the north of the country, seizing major cities and towns.

Mr Abbott praised Mr Obama's ''careful and measured response'' so far to the Iraq crisis.

He said ''no one should underestimate the seriousness of the situation in Iraq'' but added it was ''a witch's brew of difficulty and complexity'' and the West needed to carefully consider any further military response.

Iraq has asked Washington to carry out airstrikes against ISIL, which has seized swaths of the north of the country.

Mr Abbott said Australia continued to consult with the US and other allies but added that ''as far as I am aware, we have not yet been asked for any assistance''.

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