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U.S. forces moved into the heart of Fallujah (search) on Wednesday to squeeze out remaining enemy fighters in what may be a turning point in the mission "to return Fallujah to the people." Militants claimed to have captured 20 Iraqi troops amid the fighting in the restive city.

Elsewhere in Baghdad, a car bomb killed at least 10 people, and two relatives of Iraqi Interim Prime Minister Ayad Allawi (search) were kidnapped.

Lt. Gen. John Sattler, the commanding general of the 1st Marine Expeditionary Force (search) leading the Fallujah operation, said that coalition and Iraqi forces were covering every quadrant of the Sunni Muslim stronghold.

"Our mission is to make sure there are no safe havens throughout the city of Fallujah," Sattler told reporters Wednesday evening. "To perform that mission we must cover the entire city — there is no concentration on the center of Fallujah."

However, a videotape broadcast on pan-Arab satellite network Al-Jazeera on Wednesday underlined the peril Iraqi and coalition troops are in.

Twenty men wearing Iraqi National Guard uniforms were shown with their backs to the camera.

The station said a masked militant reading a statement on the tape promised not to kill the prisoners shown but threatened to kill others captured in the future.

U.S. and Iraqi forces were able to cut through Fallujah, which seemed to indicate that most insurgents and their leaders had abandoned the city before the offensive began, but Sattler stressed that those who remained would be eliminated.

"The strategy was to seal the town off before we moved in, which we did ... Because of the encirclement and coordination of all [Iraqi and coalition] forces, when [the insurgents] attempted to flee from one zone to another they were killed or captured as they moved back and forth," Sattler said. "They are now in small pockets, blind, moving throughout the city. And we will continue to hunt them down and destroy them."

U.S. forces are now in control of 70 percent of Fallujah, which insurgents forced into a narrow section flanking the main east-west highway bisecting the city, said Maj. Francis Piccoli, of the 1st Marine Expeditionary Force.

Troops were moving on that strip of territory Wednesday. "The heart of the city is what's in focus now," he said.

Earlier, at a U.S. camp outside Fallujah, government spokesman Thair al-Naqeeb said "many armed groups" in the city had asked to surrender and that Iraqi authorities "will extend amnesty" to those who have not committed major crimes.

Also on Wednesday, CDs and records of foreign captives were discovered by Iraqi soldiers in houses in the city's northern section. Sunni Muslim terrorists have claimed responsibility for a string of hostage-takings and slayings since the postwar insurgency began last April.

Officials told FOX News several of the CD-ROMs contained footage of beheadings.

The Iraqi troops "saw CDs they broadcast, and there was the name of a victim. Also there was the black clothing that you've seen in some of the TV they were broadcasting when they captured some hostages," Maj. Gen. Abdul Qader Mohammed Jassem Mohan told reporters.

The hostage records found in northern Fallujah included the names of many of the nine or more foreigners still in the hands of kidnappers — most notably, British aid worker Margaret Hassan, French journalists Christian Chesnot and Georges Malbrunot and an unidentified American worker for a Saudi company.

Violence in Baghdad

A car bomb targeting police exploded Wednesday in eastern Baghdad (search), killing at least 10 people and injuring 15 others, police said.

Police officer Qahtan Jumaygh said the 8 p.m. blast in the eastern Zaytouna neighborhood was aimed at police patrol cars, but did not injure any policemen. Dozens of cars in the area were damaged.

Earlier on Wednesday, two members of Allawi's family were reported kidnapped, possibly by insurgents seeking to open a "second front" to divert U.S. and Iraqi forces from the Fallujah offensive. The kidnapping of the prime minister's cousin, Ghazi Allawi, and the cousin's daughter-in-law may be part of the campaign.

Armed men snatched the two from their home in Baghdad Tuesday night, al-Naqeeb said. The next day a militant group calling itself the Ansar al-Jihad threatened to behead the hostages within 48 hours unless the Fallujah siege was ended.

The group's claim to be holding the captives could not be verified.

Al-Naqeeb, the government spokesman, denounced the abduction of the prime minister's two family members.

Ghazi Allawi "is 75 years old. He has no political affiliation and is not holding a government post," al-Naqeeb said.

Ansar al-Jihad claimed in a Web posting to have carried out the kidnapping and threatened to behead the hostages within 48 hours unless the siege of Fallujah was lifted and prisoners were freed.

Ansar al-Jihad said it abducted three people — a cousin of Allawi, the cousin's wife and another relative. Initial police reports, later corrected by the government, had said three people were kidnapped.

Death Toll in Fallujah Grows

At least 71 militants have been killed as of the beginning of the third day of intense urban combat, the military said. As of Tuesday night, 10 U.S. troops and two members of the Iraqi security forces had been killed. Marine reports Wednesday said 25 American troops and 16 Iraqi soldiers were wounded.

U.S. and Iraqi forces seized Fallujah's city hall compound before dawn after a gunbattle with insurgents who hit a U.S. tanks with anti-armor rockets. Iraqi soldiers swept into a police station in the compound and raised a flag above it.

Gunmen fired on troops from a mosque minaret, sparking a battle, BBC's embedded correspondent Paul Wood reported. Marines said the insurgents waved a white flag at one stage but then opened fire, prompting the Marines to call in airstrikes, Wood said.

Tank gunners opened fire on insurgents in a nearby five-story apartment building, and flames shot from several windows of the building.

Residents reported heavy clashes and artillery shelling in the Jolan and Jumhuriya neighborhood, along the central highway.

Dead bodies lay on the streets of Jumhuriya, with dogs hovering around them, witnesses said. Residents said they were running out of food in a city that had its electricity cut two days ago.

While the U.S. military acknowledged Tuesday that the most wanted man in Iraq, Abu Musab al-Zarqawi (search), had likely escaped Fallujah, Qader stressed that the terrorist was not the raison d'etre for the mission.

"The Iraqi armed forces, when they came to Fallujah, did not come to only follow and pursue Musab al-Zarqawi ... We arrived here to do a job, and we are not here to get the prize for somebody like Musab al-Zarqawi," Qader told reporters Wednesday.

Most insurgents likely fled the city before the assault began so they could fight elsewhere, officers said Wednesday. Iraqi and U.S. commanders had been warning for weeks that they would invade Fallujah to re-establish government control.

"That's probably why we've been able to move as fast as we have," said one officer from the Army's 1st Cavalry Division, who asked not to be named.

Fallujah's defenses have crumbled faster than U.S. commanders expected, With their command networks broken down, bands of three to five guerrillas were left fighting for self-preservation rather than as part of a larger force, officials said.

About 100 men, women and children made their way to American positions in the south of the city and gave themselves up Wednesday, an officer from the Army's 1st Cavalry Division said. The group was to be searched for weapons and questioned, and all military-age men would be detained, the officer said.

Most of Fallujah's 200,000 to 300,000 residents are believed to have fled the city before the U.S. assault. Civilian casualties in the attack are not known, though U.S. commanders say they believe they are low.

The U.S. advance in Fallujah was more rapid than in an offensive in April, when insurgents fought a force of fewer than 2,000 Marines to a standstill in a three-week siege. It ended with the Americans handing over the city to a local force, which lost control to Islamic militants.

This time, the U.S. military has sent up to 15,000 U.S. and Iraqi troops into the battle, backed by tanks, artillery and attack aircraft.

If reports that most gunmen fled the city are true, it indicated that while the new offensive may cost the insurgency its strongest bastion, the fighters will seek to continue their campaign of violence elsewhere.

Violence Continues Elsewhere in Iraq

In other violence in Iraq, at least 18 people were killed in fighting Wednesday, including an American soldier and a foreign contractor. Authorities clamped an immediate curfew on the northern city of Mosul as U.S. and Iraqi forces clashed with gunmen there.

Fierce fighting also took place in Baghdad and in Ramadi, a Sunni stronghold where explosions shook the city as U.S. troops and gunmen battled near the main government building.

In Mosul, the curfew came after a series of clashes including two attacks against American military convoys, U.S. Capt. Angela Bowman said. A foreign contractor was killed in one of the attacks, Bowman said, without giving details.

Smoke was seen rising above the rooftops as residents reported fighting in western districts. Three Iraqi policemen and an Iraqi National Guard soldier were killed, hospital and security officials said.

In Baghdad — where Allawi this week imposed a nighttime curfew for the first time in a year — U.S. troops and masked fighters traded fire, wounding four bystanders. Six people were killed and four others wounded during clashes between U.S. soldiers and insurgents in Latifiyah, south of Baghdad.

A U.S. soldier was killed and another wounded by a roadside bomb north of Baghdad on Wednesday, and a bomb killed six Iraqi soldiers in northern Iraq. At least 13 Americans have been killed in attacks outside Fallujah since Monday.

The Associated Press contributed to this report.