An audio recording attributed to Usama bin Laden (search) offered rewards in gold Thursday for the killing of top U.S. and U.N. officials in Iraq or of the citizens of any nation fighting there.

The 20-minute recording, dated Thursday, appeared on two Web sites known for militant Islamic messages. The voice sounded like that of bin Laden and the words were laden with Quranic verse, but the authenticity of the recording could not immediately be verified.

The CIA is looking into the statement, a spokesman said, speaking on the condition of anonymity.

"You know that America promised big rewards for those who kill mujahedeen [holy warriors]," the speaker said. "We in Al Qaeda organization will guarantee, God willing, 10,000 grams of gold to whoever kills the occupier Bremer, or the American chief commander or his deputy in Iraq."

He was referring to L. Paul Bremer (search), the chief U.S. administrator in Iraq, and top military officials.

"For security reasons, the rewards will be given as soon as conditions permit, God willing," the voice said. "As for those who die while killing an occupying solider, the great prize will be for us and for him when God grants him martyrdom, and the smaller prize [the gold] will be for his family."

The United States has offered rewards of its own for information leading to the captures or deaths of bin Laden and his top lieutenants, as well as for top figures in the former Iraqi government of Saddam Hussein (search). The price on bin Laden's head now stands at $50 million -- far more than the nearly $125,000 that 10,000 grams of gold is worth.

The recording promised the same reward for the deaths of U.N. Secretary-General Kofi Annan (search) and his envoy to Iraq, Lakhdar Brahimi.

"The United Nations is nothing but a Zionists' tool, even if it worked under the cover of providing humanitarian aid," the voice said. "... Whoever kills Kofi Annan or the head of his commission in Iraq or a representative like Lakhdar Brahimi, he will be awarded the same prize of 10,000 grams of gold."

The speaker promised a lesser prize -- 1,000 grams of gold -- to anyone killing a citizen of countries he called "the masters of the veto like Americans and Britons" -- a reference to nations with veto power on the U.N. Security Council.

And he offered 500 grams of gold to anyone killing citizens of countries he called "slaves of the Security Council who are in Iraq, like Japan and Italy."

The context indicated the rewards applied to citizens of those countries who are in Iraq.

With gold selling Thursday on London exchanges for $387.60 a troy ounce, 10,000 grams of gold was valued at $124,630, 1,000 grams at $12,463, and 500 grams at $6,231.

It appeared to be the first publicized offer by bin Laden for rewards for the deaths of his enemies. However, a U.S. joint congressional intelligence panel said in a report two years ago that bin Laden had agreed in 1998 to allocate $9 million in reward money for the assassination of top U.S. intelligence agency officers.

Bin Laden had never been known to offer rewards for missions he had described as followers' religious duty to carry out.

The recordings appeared on Web sites for the Ansar Islam Forum and the Islamic Research Center. Both are clearing-houses for statements by Al Qaeda and other Islamic militant groups. The forum also has a bulletin board on which extremists chat and comment on the statements.

The speaker denounced U.S. plans to hand sovereignty to Iraqis on June 30, calling them a trick to end the resistance that has killed hundreds of U.S. soldiers.

"There is no sovereignty for Iraq as long as a crusader solider remains in its land, and no sovereignty for Iraq as long as it is not ruled by Islam," the voice said.

The speaker urged Iraqis to fight a holy war against their U.S.-appointed Governing Council.

He also threatened any Iraqis helping the U.S.-led coalition.

"Whoever helps the infidels against Muslims, or helps the occupying forces and whatever is affiliated to them -- such as the transitional or permanent government -- is committing a violation to Islam," he said, warning of consequences including "spilling blood, taking his money, separating him from his wife."

The recording was titled: "A Word from the emir of the Islamic armies, Usama, to the nation and especially to brotherly Muslims in Iraq."