Defence Minister David Johnston has strongly suggested any military role by Australia in Iraq could include providing intelligence on the radical group that has taken control of major cities in a lightning offensive.

Senator Johnston flagged a decision in the next 72 hours in close consultation with allies the United States, who will take the lead in helping the Iraqi government beat back the Sunni insurgents, with help from Australia.

Asked what Australia could contibute, particularly after ground troops have been ruled out by US President Barack Obama, Senator Johnston twice mentioned intelligence when questioned by reporters on Monday morning in Canberra.

''We'll see what role (the US) would have us play in that,'' he said. ''I think having said no boots on the ground, it’s an intelligence assistance role that we would be seeking to assist them with. But let’s just see how this plays out.''

Later he added: ''What role Australia will take in that will evolve over time but I suspect . . . it will be an intelligence-based role.''

It remains unclear what kind of intelligence Australia might provide and whether this could include aerial surveillance. Australia currently operates Heron surveillance drones out of Afghanistan. It also has P-3 Orion surveillance planes, which are primarily for maritime surveillance but have been used successfully in Afghanistan by the US.

Senator Johnston added that Australia and the US needed to ''let the dust settle for a few days'' to see how the Iraqi government itself was handling the problem.

But he also said that ''we'll see the response in the next few days''.

Mr Obama has stressed that the Iraqi government needs to prove it can govern more equitably, and thereby reduce anger among minority Sunnis, before the US gets involved.

The US is reportedly mulling air strikes against the Sunni jihadist group, the Islamic State of Iraq and the Levant and has moved an aircraft carrier into the Persian Gulf.

Asked whether there might be risks in air strikes, Senator Johnston said: ''In the last 10 to 15 years we have developed very, very good skills on precision munitions. But let’s not speculate on the risks . . . Let’s just sit down, analyse what the government of Iraq is able to do, what the situation plays out to be and then, with . . . the Coalition partners, we formulate a strategy.''

Senator Johnston also echoed Foreign Minister Julie Bishop in saying that Australia was poised to evacuate diplomatic staff at very short notice if they were at risk.

''We're on a very, very close watching brief with respect to this organisation (ISIS) which to some extent has taken particularly the Iraqi government by surprise. (They’re) clearly very organised, very capable,'' he said.

He declined to say whether Australia might provide broader help by evacuating other countries’ nationals as well.

Ms Bishop also said on Monday that Australia stood ready to supply humanitarian aid to Iraq and has begun evacuating staff from diplomatic posts in Baghdad.

The Minister has also reissued pleas for Australians visiting the country to leave immediately, if it is safe to do so, via the commercial airport in Baghdad.

She said the government was aware of more than 90 Australians in Iraq and said her "strong advice" was that they should leave.

''The international airport in Baghdad continues to operate normally,'' she said.

''There are commercial flights available, indeed, Turkish airlines has announced additional flights.

''I do reiterate advice that Australians in Iraq should depart immediately.''

Ms Bishop said Australians concerned about family and friends in Iraq should try to contact them directly as consular assistance had been reduced because of the crisis.

People unable to do so are encouraged to call the Department of Foreign Affairs and Trade's 24-hour consular emergency centre on 1300 555 135, or +61 2 6261 3305 if calling from overseas.

with Lisa Cox

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