In Baghdad, a 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.
South of the capital, 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. Hospital officials said at least 14 people were killed.
It was a day in which at least 30 people died in politically motivated violence across the country - stark testimony to a security situation threatening to spiral out of control even as January's scheduled elections approach.
Late Saturday, the decapitated body of a young Asian male was found in an insurgent-infested neighborhood of Baghdad, and hospital officials and police believed it was that of, although his identity had not been confirmed.
An al Qaeda-linked group led by Jordanian-born terror mastermind Abu Musab al-Zarqawi had threatened to behead the 24-year-old Japanese backpacker unless Tokyo withdrew its soldiers from Iraq.
Later Saturday, apleaded for her life and asked Poland to remove its troops from Iraq in a video aired by Al-Jazeera television.
Teresa Borcz Khalifa, a 54-year-old with dual Polish-Iraqi citizenship, was wearing a black top and sitting in front of a banner with the militant group's name, Abu Bakr al-Siddiq Fundamentalist Brigades.
In other developments:
The Marine deaths came when a car bomb went off next to a truck southwest of Baghdad, between the capital and Fallujah, said Maj. Clark Watson, with 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 the rebel bastion of 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, military officials have said.
On Saturday, insurgents fired mortars at Marine positions outside Fallujah. U.S. troops responded with "the strongest artillery barrage in recent weeks," according to Marine spokesman 1st Lt. Lyle Gilbert.
Later in the afternoon, 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.
Crowds of Iraqis peered skyward as a pair of warplanes circled over the rebel-held city, where large explosions rumbled Saturday afternoon. Insurgents fired rockets and mortars toward U.S. Marine positions.
"This is very painful for Fallujah. I think they're destroying the town and killing families there," said Saadoun Mohamed, a 35-year-old driver near Fallujah.
"It's very complicated. I don't know how to solve this problem," he said through an Iraqi Marine translator.
Clashes between U.S. troops and insurgents also broke out Saturday in Ramadi, west of Fallujah. Hospital officials said two policemen were killed and four Iraqis injured in the crossfire, said Dr. Saleh al-Duleimi of the Ramadi General Hospital.
On the tape that surfaced Saturday, Polish hostage Khalifa said, "Once again I call on you to help me, by saving my life. My life is in great danger. The one thing that will save my life is any response to the Iraqis' demands: by first getting the Polish troops out of Iraq and second, giving any help to release the female Iraqi prisoners from the various American prisons in Iraq."
Poland commands about 6,000 troops from 15 nations - including some 2,400 from Poland - in central Iraq. The Warsaw government has ruled out any possibility of negotiations or a pullout from Iraq.
In Baghdad, a hospital official said he believed the beheaded body found Saturday was that of kidnapped Japanese hostage Shosei Koda, saying he recognized the features from a videotape aired by Al-Jazeera television.
Policeman Yassin Hashim, who examined the body, said it was dressed in jeans, a beige shirt, and black underwear, he said. His hands and legs had been bound with white rope, he said.
The victim had long black hair and Asian facial features, with a scar near his heart, Hashim said. He said he believed the death occurred recently.
"I am the one who examined the body and I confirm that he is the Japanese person who appeared on television and was threatened to be beheaded," he said.
Japan is aware of the report and is trying to confirm its details, Foreign Ministry spokesman Akira Chiba said.
A day after the militant's apparent deadline, the U.S. military discovered a body between the towns of Balad and Tikrit that apparently shared several features with Koda.
But a Japanese doctor who examined the body in Kuwait after it was flown there by the U.S. military said it appeared to belong to a man in his 50s with starkly different features than Koda.
Also in the capital, the car bomb that exploded outside the office of the Al-Arabiya television network, a satellite broadcaster based in Dubai, United Arab Emirates, killed seven people injured 19, according to police and hospital officials.
Al-Arabiya's managing editor, Abdulrahman al-Rashed, said seven people remained missing following the bombing.
A militant group calling itself the "1920 Brigades" claimed responsibility for the attack, blasting Al-Arabiya as "Americanized spies speaking in Arabic tongue" in a statement posted on the Web. The station is owned by Saudi investors.
"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-Rashed - who has been an outspoken critic of Islamic militants and terror attacks - said the station will continue to operate from Iraq. "This is our job and we won't succumb to pressure," he said from Dubai.
The Iraqi police shooting south of Baghdad came after an American convoy was attacked early Saturday with roadside bombs, witnesses said. After the Americans pulled out, Iraqi police and National Guards arrived on the scene and began firing wildly, the witnesses said. The U.S. military had no immediate comment.
Three minibuses and three vans were hit on the street near the town of Haswa, 25 miles south of the capital, the witnesses said.
Abdul Razzaq al-Janabi, director of Iskandariyah General Hospital, said 14 people were killed and 10 others injured. More wounded were taken to other hospitals. Reporters saw bloody bodies riddled with bullet holes inside the buses.
In Baghdad, Mohammed Bashar al-Faydhi, a spokesman for the influential Association of Muslim Scholars, demanded a government investigation into "this massacre" because "Iraqi policemen are carrying out such crimes."
Al-Faydhi also said that a bid to mediate a peaceful solution to the Fallujah standoff had failed because of the government's demand that the city hand over extremists, including al-Zarqawi. Hardline clerics who run the city said al-Zarqawi isn't there.
"There is no good news on the horizon in finding a solution," al-Faydhi said. "There is a belief among the Fallujah people that the Americans will invade the city even if the Arab fighters leave."
Marines mounted a three-week siege of Fallujah in April but called off the offensive after a public outcry over civilian casualties. The siege was launched after militants ambushed and killed four American contractors, mutilated their bodies and hung them from a bridge.
This time, U.S. officials insist that the final order for an all-out attack will come from Iraqi Prime Minister Ayad Allawi and that Iraqi forces will join the fight. American officials estimate up to 5,000 Islamic militants, Saddam Hussein loyalists and common criminals are holed up in Fallujah.