Near Fallujah, Iraq ? A car bomb killed eight U.S. Marines outside Fallujah on Saturday, the deadliest attack against the U.S. military in nearly six months. Marines pounded guerrilla positions on the outskirts of Fallujah, where American forces are gearing up for a major assault on the insurgent stronghold.

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

In Baghdad, another car bomb exploded outside an Arabic television network’s offices, killing seven people and injuring 19 in the biggest attack against a news organization since the occupation began last year.

It was a day in which at least 30 people died in politically motivated violence across the country — stark evidence of a security situation threatening to spiral out of control.

Late Saturday, the decapitated body of Japanese hostage Shosei Koda, 24, was found in an insurgent-infested neighborhood of Baghdad. The Japanese Foreign Ministry confirmed Koda’s identity through fingerprints.

An al-Qaida-linked group led by Jordanian terrorist Abu Musab al-Zarqawi threatened to behead the Japanese backpacker unless Tokyo withdrew its soldiers from Iraq. Japan rejected that demand.

“It is to our great sorrow that after putting all our efforts into securing his release he has become a victim of terrorism,” Foreign Minister Nobutaka Machimura said Sunday in Tokyo. “We cannot allow this kind of action. Japan, in cooperation with the international community …, must continue the battle against terrorism.”

South of Baghdad, witnesses said a U.S. convoy came under attack, prompting Iraqi forces to open fire randomly and throw hand grenades, hitting three minibuses and three vans. At least 14 people were killed, hospital officials said.

The Marine deaths came when a car bomb went off next to a truck southwest of Baghdad, said Maj. Clark Watson of the 1st Marine Expeditionary Force. Nine other Marines were wounded in the attack in western Anbar province, which includes Fallujah and other insurgent strongholds, the military said.

It was the biggest number of American military deaths in a single day since May 2, when nine U.S. troops were killed in separate mortar attacks and roadside bombings in Baghdad, Ramadi and Kirkuk.

American forces are preparing for a major assault on Fallujah in an effort to restore control to a swath of Sunni Muslim towns north and west of the capital ahead of crucial national elections due by Jan. 31.