Contract killers are being offered as little as $US50 ($67) to hunt down coalition troops - including Australians - in Iraq.
The mercenaries are being wooed from poor neighbouring countries in the Middle East with the promise of cash payments for every Western soldier killed.
Air Commodore Greg Evans, who took command of Australian forces in the Middle East three weeks ago, told Sydney newspaper The Sunday Telegraph that Iraqi insurgents were turning to hired assassins to do their dirty work.
"This is a difficult adversary. The insurgency is not a coherent force," Air Commodore Evans told the newspaper.
"We are seeing zealots brought in from outside Iraq and paid $US50 for contract killings. These forces are a general threat to the coalition."
The commander said the 350 Australian troops under his control in Iraq were preparing for an all-out assault by insurgents in the lead-up to the country's first elections, expected to be held on January 30.