The Marines later reported a ninth combat death Saturday but did not say whether it was in the car bombing or another action, The Associated Press reported. Efforts to contact the Marines for clarification were unsuccessful.

In Baghdad, insurgents staged their first major assault on a news media organization by detonating a car bomb outside the offices of a popular Arab news network, killing at least seven people and wounding about 19 others, police and hospital officials said.

The attack on the Marines took place near Abu Ghraib, the prison 15 miles west of Baghdad used by the Americans to hold detainees, said Capt. Bradley Gordon, a Marine spokesman. The military said in a terse statement that those killed were conducting ''increased security operations.'' Marines have been battling an increasingly lethal insurgency in rebellious Anbar province, which encompasses the parched lands of western Iraq and includes the provincial capital of Ramadi and the insurgent stronghold of Fallujah.

The bomb that killed seven in Baghdad exploded outside the offices of Al-Arabiya, the prominent network based in the United Arab Emirates. Insurgents drove a car packed with explosives right up to the network's offices in Mansour, an affluent neighborhood west of the Tigris River that has suffered from a surge of violence.

An hour after the blast, a charred car chassis lay in the road as U.S. soldiers and Iraqi policemen raced to cordon off the site. Ambulances carried off bodies drenched in blood.

A group calling itself the 1920 Brigades claimed responsibility in an Internet posting, saying that the network's workers were ''Americanized spies speaking in Arabic tongue.'' Al-Arabiya has covered the war with an anti-American angle and has been sharply criticized by Defense Secretary Donald Rumsfeld.

A decapitated body wrapped in an American flag and found in an insurgent-controlled section of Baghdad was that of a Japanese man kidnapped by Islamic militants, a Japanese official said today, The Associated Press reported. Foreign Minister Nobutaka Machimura said in Tokyo that the government had confirmed that the body found Saturday was that of Shosei Koda, 24, a Japanese traveler being held by the militant group of Jordanian fighter Abu Musab al-Zarqawi.

''It is to our great sorrow that after putting all our efforts into securing his release he has become a victim of terrorism,'' Machimura said.

''We cannot allow this kind of action. Japan, in cooperation with the international community . . . must continue the battle against terrorism.''

The deaths of the eight Marines came as the American military was making final preparations for an all-out invasion of Fallujah, the center of the Sunni-led insurgency and a suspected haven for Zarqawi. Warplanes struck southern Fallujah on Saturday as artillery pounded the area. There was no immediate report of casualties.

In the besieged city, a council of tribal and religious leaders awaited the arrival of a delegation from the interim National Assembly, which has been charged with helping negotiate a peace settlement and averting the planned American invasion. Peace talks have been continuing in spurts over the past few weeks, although neither side has expressed any optimism.

The number of U.S. troops killed Saturday was the largest in a single day since May 2, when nine troops died in attacks across the country.

In early April, 12 Marines were killed in an ambush in Ramadi. Right after that ambush, the military said the Marines had been killed in an insurgent attack on a base or outpost. But in recent interviews, Marines with the 2nd Battalion, 5th Marines, which took charge of Ramadi in early September, said guerrillas had killed the 12 Marines in a roadway ambush while they were riding in unarmored or very lightly armored vehicles.

Since then, insurgents have used car bombs with deadly effect against U.S. troops. On Sept. 6, one such bomb tore through a convoy carrying American and Iraqi troops near Fallujah, killing seven Marines and three Iraqi security officers. Four months earlier, a car bomb killed eight soldiers from the 1st Armored Division near Mahmudiya, south of Baghdad.

The bomb outside the Al-Arabiya office in Baghdad exploded in the midafternoon, with the blast heard for miles. The explosive-laden car had pulled up to the gate, about 9 to 13 feet from the office building itself, said Najwa Qasim, a correspondent for the network. A deep pit marked the spot where the bomb went off. Large parts of the building collapsed, and at least three staff members were killed, Qasim said.

Al-Arabiya's offices are surrounded by the homes of Iraqi officials and are just blocks from the residence of Adnan Pachachi, a prominent member of the former Iraqi Governing Council. A recruiting center for the Iraqi police sits nearby, and U.S. soldiers in Humvees often patrol the leafy suburb.

The Mansour District has grown increasingly dangerous in recent weeks. A car bomb exploded there last month, and two U.S. engineers and a Briton were kidnapped from their home around the same time and later beheaded by Zarqawi's group.