Eight U.S. Marines were killed and nine others wounded Saturday in the Sunni Triangle area near Baghdad, the military announced.
It was one of the highest U.S. casualty figures in months in a single incident.
The Marine casualties came when a car bomb went off next to a truck southwest of Baghdad, Maj. Clark Watson of the 1st Marine Expeditionary Force told the Associated Press late Saturday.
The Marines are preparing for a decisive battle in the cities of Fallujah and Ramadi in Anbar Province, where the incident occurred and U.S. warplanes have been pounding Fallujah for weeks.
On Saturday, insurgents fired mortars at Marine positions outside Fallujah. U.S. troops responded with "the strongest artillery barrage in recent weeks," Marine spokesman 1st Lt. Lyle Gilbert told wire service reporters.
Later, a Marine Harrier jet bombed a guerrilla mortar position inside Fallujah, then strafed it with machine-gun fire, Gilbert said. He had no reports of insurgent casualties
Separately, news services reported that a car bomb exploded outside the offices of the Al-Arabiya television station in central Baghdad on Saturday, killing seven people and wounding 19.
The car bomb detonated near the Dubai-based network's building in the western Mansour neighborhood of the capital, Police Lt. Ziad Tareq told the Associated Press.
Network correspondent Najwa Qassem said the injured included technicians and drivers. Police said bystanders were also hurt in the blast.
A militant group claimed responsibility for the attack on Al-Arabiya's offices. In a statement posted Saturday on a Web site clearinghouse, the group identifying itself as the "1920 Brigades" said it brought down the building of the "Americanized spies speaking in Arabic tongue."
"We have threatened them to no avail that they are the mouthpiece of the American occupation in Iraq," the statement said. It warned of more attacks against this "treacherous network." It was impossible to verify the claim's authenticity.
Al-Arabiya's general manager, Abdulrahman al-Rashed, has been a vocal critic of Islamic militants and terror attacks.
Insurgents have controlled Fallujah since April, when Marines laid siege to the city, but an offensive was called off under pressure from the White House and L. Paul Bremer, the civilian administrator of the U.S.-led occupation authority then in charge in Iraq. Since then, military officials have described Fallujah as a hub of the Iraqi insurgency and the base for Abu Musab Zarqawi, a Jordanian militant who has proclaimed allegiance to Osama bin Laden's al Qaeda organization.
While Zarqawi and other foreign militants have vowed to fight until U.S. and other occupying forces quit Iraq, local insurgents have been negotiating with Iraqi authorities to hand over control of the city peacefully. But Taha Ali, a press officer for interim Iraqi Prime Minister Ayad Allawi, said Friday that the government was "losing patience" with the discussions.
Allawi favors the "peaceful solution," Ali said, but added that "this might be the last" chance to accept it.
On Friday in Fallujah, about 50 religious leaders met with members of the Shura Council of Mujaheddin, the self-appointed group that governs the city. The council closed the meeting to reporters, but a source familiar with the discussions said the group agreed to issue a fatwa, or religious order, calling for a holy war if U.S. forces pushed into Fallujah.
"War is very close," Abdullah Janabi, the head of the council, said while leading Friday prayers at the Hadhra Muhammadiya mosque, one of the most important in Fallujah.
"The government is responsible for the bloodshed in Fallujah," he said. "We have no choice -- it is either victory or martyrdom."
Barbash reported from Washington.