The U.S. Embassy, meanwhile, said a rocket attack on Iraq's Green Zone on Wednesday killed four foreign contractors —one from the Philippines, one from Nepal and two from India — who were working for a U.S. government contractor. It was the third straight day that extremists used rockets or mortars to hit the area where Iraq's parliament meets.

U.S. Maj. Gen. William Caldwell said the killing of Muharib Abdul-Latif al-Jubouri, described as al-Qaida's information minister, had apparently led to confused reports that al-Qaida's top leader or the head of an umbrella group of Sunni insurgents had been killed.

Caldwell said the military had conducted numerous operations against al-Qaida in Iraq in the last six days but does not have the bodies of Abu Omar al-Baghdadi and Abu Ayyub al-Masri and did not know "of anybody that does."

U.S. and Iraqi forces have stepped up operations against the terrorist network following a series of car bombings and suicide attacks that have killed hundreds in recent weeks despite a security crackdown in Baghdad and surrounding areas.

Al-Jubouri was killed while trying to resist detention in an operation about four miles west of the Taji, a town near an air base north of Baghdad early Tuesday, and the body was initially identified by photos, then confirmed by DNA testing Wednesday, he said.

Al-Jubouri was believed to have been deeply involved with the kidnapping of Jill Carroll, the Christian Science Monitor reporter who was released unharmed, and Tom Fox of Clear Brook, Va., one of four men from the Chicago-based peace group Christian Peacemaker Teams who was found shot to death in Baghdad on March 10, 2006, he said. He was also involved in the kidnapping of two Germans in January 2006, Caldwell said.

In a statement, Christian Science Monitor Editor Richard Bergenheim said the development "reminds us of the enormous efforts made by everyone over 82 days to secure Jill's safe release."

"While much remains to be done to improve conditions in Iraq, we appreciate the continuing efforts by the U.S. military and the Iraqi government to make the country a safer place for journalists and citizens alike," Bergenheim said.

Today, mourners gathered at al-Jubouri's house in Duluiyah, 45 miles north of Baghdad, as a huge funeral tent went up in the street, police said.

The Interior Ministry said earlier that al-Baghdadi, the head of the Islamic State of Iraq, had been killed and released photos of what it said was the body of the leader of the umbrella group, which includes al-Qaida.

But Caldwell said al-Baghdadi's death could not be confirmed.

"If that person even exists, again, we have nobody in our possession or know of anybody that does, alive or dead, that is going through any kind of testing or analysis at this point with respect to those two individuals," he said.

On Tuesday, officials said al-Masri, the head of al-Qaida in Iraq, had been killed by rivals north of Baghdad, but the body had not been recovered.

Regarding al-Masri, Caldwell said "we in fact do not have in our possession nor do we know of anybody that has anybody or person at this time that we think is him."

"His overall status whether he is dead or alive is actually unknown to us at this point," he added.

The U.S. Embassy statement gave no other details about Wednesday's attack that killed the four contractors in the Green Zone, which is home to the U.S. and British embassies and thousands of American troops as well as key Iraqi government offices.

Insurgents routinely fire rockets and mortar rounds into the sprawling Green Zone.

The attacks seldom cause casualties or damage because they are poorly aimed and there is a lot of open space in the zone, but two Americans — a contractor and a soldier — were killed in March in a rocket attack on the area and two suicide vests were found unexploded less than a week after that.

The adequacy of security in the area also came into question after the April 12 suicide bombing in the parliament building's dining hall. One lawmaker was killed in the blast, which was claimed by an al-Qaida-led amalgam of Sunni insurgents.