Rewards of gold are on offer for the killings of top US and UN officials in Iraq, according to a message purportedly from Osama Bin Laden.
Bin Laden has a $27m bounty on his head
It promised 10kg (22lb) of gold to anyone killing US administrator Paul Bremer or UN envoy Lakhdar Brahimi, as well as UN chief Kofi Annan.
The message also declared jihad, or holy war, on the interim government due to take power in Iraq on 30 June.
The CIA said the voice in the recording on the internet was "likely" Bin Laden.
The message was posted on a website known to be used by Islamist militants.
It called on Muslims in Iraq to "raise the flag of jihad" against "the crusaders" - meaning foreign forces in Iraq - and against "the infidel government and its supporters".
Observers say the statement used language similar to previous statements from the al-Qaeda leader, laden with Koranic verse.
But they add that he has never before offered rewards for missions which he considers to be a religious duty, nor has he singled out particular people as targets.
Change of strategy
"It is unprecedented, because in the past, al-Qaeda always said, 'Kill the Americans, kill the Westerners,' but did not specifically name individuals," terrorism expert Rohan Gunaratna told the BBC World Service's World Today programme.
"In that sense, this is a change from the overall strategy of al-Qaeda," said Mr Gunaratna, who is head of terrorism research at the Institute of Defence and Strategic Studies in Singapore.
"We in al-Qaeda organisation will guarantee, God willing, 10,000g of gold to whoever kills the occupier Bremer, or the American chief commander or his deputy in Iraq," the message said.
The reward is equivalent to about $125,000.
Smaller rewards of 1kg of gold were offered for the deaths of ordinary Americans and Britons, and half that was pledged for the killings of citizens of Japan and Italy, who were called "slaves" of the UN Security Council.
"For security reasons, the rewards will be given as soon as conditions permit, God willing," the statement said.
The US has offered a $27m bounty for the capture or killing of Bin Laden.