A statement from U.S. Central Command said the incident occurred Thursday morning and that the names of the dead and wounded were being withheld pending notification of relatives.
It gave no further details.
The announcement capped a day of back-to-back attacks on U.S.-led occupations in Iraq that killed two U.S. soldiers and wounded 14. Two U.S. soldiers were also reported abducted in Baghdad.
In addition, two Iraqis were killed Thursday when a U.S. led-convoy in which they were traveling came under a grenade attack.
Between Wednesday and Thursday, assailants blew up a U.S. military vehicle with a roadside bomb, dropped grenades from an overpass, destroyed a civilian SUV traveling with U.S. troops, blew up an oil pipeline and fired an apparent rocket-propelled grenade at a U.S. Army truck.
Earlier, U.S. soldiers at the scene of an attack in southwest Baghdad said one of their colleagues had been killed when an explosive device went off on the road leading to Baghdad International Airport.
It was not immediately clear if the death reported by Central Command was referring to the same incident.
In a separate incident, a U.S. Marine was killed and two others hurt when their vehicle rolled over as they were speeding to the scene of yet another attack.
In other developments:
Thursday's attacks came two days after the killing of six British military police, and only a few hours after the Arab television network Al-Jazeera reported receiving a statement from a group claiming responsibility for recent attacks on allied forces in Iraq.
Al-Jazeera says the statement and videotape come from an Iraqi resistance group that's promising more attacks.
This is the first time that any group has publicly claimed to behind attacks on allied forces who have come under fire since May 1st, the date when President Bush declared major combat in Iraq to be over.
The statement broadcast by al-Jazeera comes from a previously unheard-of group calling itself the Mujahedeen of the Victorious Sect. The videotape shows what the announcer says was an attack by the group on American military vehicles.
On Wednesday afternoon, ambushers dropped grenades from a Baghdad overpass onto a passing convoy of Army Humvees, said Marine Corps Maj. Sean Gibson. There were no serious injuries.
In Hilla, 45 miles south of Baghdad, three Marines were wounded Wednesday in an ambush, a U.S. military statement said. One Marine was killed and two were injured when their vehicle — part of a quick reaction force dispatched in response to the ambush — rolled over on the soft shoulder on the way to the scene.
Also Thursday, two Iraqi employees of the national electricity authority were killed when their U.S.-led convoy came under a grenade attack in west Baghdad, U.S. soldiers and Iraqi police said.
The convoy included U.S. Humvees at the front and the back and two Iraqi civilian vehicles in the middle. The soldiers and Iraqi police said the two Iraqis who were killed were traveling in the same car.
U.S. troops evacuated the two bodies from the badly damaged vehicle, which was covered with blood and broken glass.
None of the names of the injured or killed Americans were available.
At least 19 U.S. soldiers have died in hostile fire since major combat was officially declared over in May.
The six British soldiers were killed Tuesday in southern Iraq during a shooting rampage by townspeople furious over the killing of four neighbors during a demonstration, apparently at the hands of British troops.
That attack, in the town of Majar al-Kabir, 180 miles southeast of Baghdad, had shattered the peace that had reigned in Shiite-dominated southern Iraq since the fall of Saddam Hussein — and spurred British authorities to consider requiring troops to wear body armor and helmets.
On Thursday, 11 pickup trucks filled with armed men from the local security force patrolled the city on their own, with no British troops in the town center.
Recent attacks on U.S. forces near Baghdad have been blamed on remnants of Saddam's regime or his Sunni followers, but the Majar al-Kabir attack came in the mostly Shiite south, where resentment toward Saddam Hussein's government had been strong.
The Shiite gunmen were enraged by the death of their neighbors — allegedly at the hands of British troops during a demonstration earlier in the day — and over weapons searches in homes with women.
On Tuesday, about 100 residents protested the British weapons sweeps in a four-hour demonstration outside the mayor's office, where a dozen British troops were posted, witnesses said. Protesters threw rocks, and British troops fired back with rubber bullets before switching to live ammunition, the witnesses said.
Local police said four Iraqis were killed, and that armed residents then killed two British military policemen. Then, witnesses said, some Iraqis went to their homes to get weapons. At least 20 armed Iraqis stormed the police station, where four British military police were located along with Iraqi policemen.
British forces in Iraq have been reduced from 45,000 during the war to 15,500 now, two-thirds of them ground forces. The United States has brought home some 130,000 troops from the region; 146,000 American forces remain in Iraq.