Australia will "in coming days" join ally the United States in an international effort to transport weapons to Kurdish forces fighting ISIL extremists in northern Iraq.

While Abbott has insisted Canberra will not be sending combat troops to the conflict, he has stepped up his rhetoric against the ISIL, calling it a "death cult" carrying out ethnic cleansing.

On Tuesday he compared them to the Nazis and communists.

"The difficulty here is that these people do exalt in death; they absolutely revel in killing," he told Sydney radio station 2GB.

"We've seen in the century just gone, the most unspeakable things happen, but the atrocities that were committed by the Nazis, by the communists and others, they were ashamed of them, they tried to cover them up.”

"This mob, by contrast, as soon as they've done something gruesome and ghastly and unspeakable, they're advertising it on the Internet for all to see which makes them, in my mind, nothing but a death cult.

"That's why I think it's quite proper to respond with extreme force against people like this."

ISIL has prompted widespread concern as it advances in Syria and Iraq, killing hundreds of people, including in gruesome beheadings and mass executions.

Abbott's comments came as a senior UN rights official said ISIL had carried out "acts of inhumanity on an unimaginable scale".

Australia is gearing up to fly a C-130 aircraft to the Iraqi capital Baghdad for customs clearance "in coming days", before heading to Kurdish-controlled Erbil. The plane will then reportedly land to hand over weaponry, which will include mortars and rocket-propelled grenades.

The dangers faced by Australian and allied forces was highlighted Tuesday with a report that a C-130 Hercules came under machine-gun fire as it dropped aid to Amerli.

Abbott said he had not been fully briefed on what might have happened.

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