BAGHDAD, Sept. 5 -- Fighters loyal to militant leader Abu Musab Zarqawi asserted control over the key Iraqi border town of Qaim on Monday, killing U.S. collaborators and enforcing strict Islamic law, according to tribal members, officials, residents and others in the town and nearby villages.

Residents said the foreign-led fighters controlled by Zarqawi, a Jordanian, apparently had been exerting authority in the town, within two miles of the Syrian border, since at least the start of the weekend. A sign posted at an entrance to the town declared, "Welcome to the Islamic Republic of Qaim."

In other developments Monday, the U.S. Army warned noncombatants to leave a portion of the northeastern city of Tall Afar ahead of an expected assault on an insurgent stronghold there. Car bombs and other political violence around Iraq killed at least 33 Iraqi civilians and security force members. A U.S. soldier and two British troops also were killed, officials said.

The report from Qaim, about 200 miles west of Baghdad, marked one of insurgents' boldest moves in their cat-and-mouse duels with U.S. Marines along the Euphrates River. U.S. forces have described border towns in the area as a funnel for foreign fighters, arms and money into Iraq from Syria.

Insurgents have occasionally made similar shows of force, such as the takeover of a Baghdad neighborhood for a few hours late last month by dozens of gunmen. They then slipped away, having made the point that they can muster men as well as plant bombs. The weekend takeover of Qaim extended already heavy insurgent pressure on the people there and came after the U.S. military said it had inflicted heavy bombing losses on foreign-led fighters.

Marines conducted heavy airstrikes in the past week on suspected insurgent safe houses in the area. Ground fighting has also been reported between Zarqawi's group and Sunni Arab tribes more open to the Iraqi government and U.S. military.

Capt. Jeffrey Pool, a Marine spokesman in Ramadi, capital of the western province that includes Qaim, said he had no word of unusual activity in Qaim. Marines are stationed just outside the town, and no Iraqi government forces are posted inside, Pool said.

Witnesses in Qaim said Zarqawi's fighters were killing officials and civilians whom they consider to be allied with the Iraqi and U.S. governments or anti-Islamic. On Sunday, the bullet-riddled body of a young woman dressed in her nightclothes lay in a street of Qaim. A sign left on her corpse declared, "A prostitute who was punished."

Zarqawi's fighters have shot and killed nine men in public executions in the city center since the start of the weekend, accusing the men of being collaborators with U.S. forces, said Sheik Nawaf Mahallawi, a leader of the Albu Mahal, a Sunni Arab tribe that had clashed earlier with the foreign fighters.

Dozens of families were fleeing Qaim every day, Mahallawi said.

For local fighters now, "it would be insane to attack Zarqawi's people, even to shoot one bullet at them," the tribal leader said. "We hope the U.S. forces end this in the coming days. We want the city to go back to its normal situation."

Many of the towns along the river have been subject to domination by foreign-led fighters, despite repeated Marine offensives in the area since May. Residents and Marines have described insurgents escaping ahead of such drives, and returning when the offensives end.

The U.S. attacks are credited with helping disrupt insurgent networks and reducing the number of car bombings and suicide attacks in the rest of Iraq.

U.S. and Iraqi officials in recent weeks have welcomed reports of local Sunni Arabs challenging the presence of foreign fighters. But the accounts from Qaim indicated a setback.

The Albu Mahal tribe remained in control of its village outside Qaim, residents said. However, a car bomb placed by Zarqawi's fighters killed a tribal leader, Dhyad Ahmed, and his son on Sunday, said a resident, Mijbil Saied.

Fighters loyal to Zarqawi openly patrolled the streets of Qaim with AK-47 assault rifles and grenade launchers. The fighters included both Iraqis and foreigners, including Afghans. They draped rooftops with Zarqawi's al Qaeda in Iraq banner of a yellow sun against a black background.

Residents said insurgents in recent weeks had begun enforcing strict Islamic law, burning shops that sold CDs and a beauty parlor, and lashing men accused of drinking alcohol. They said Zarqawi's fighters were killing government workers but had spared doctors and teachers.

Karim Hammad Karbouli, 46, said he had stood among small crowds of nervous residents watching the insurgents, waiting Sunday for his brother to come with a pickup truck so they could load up his household and leave. Karbouli said he feared both Zarqawi's fighters and U.S. bombs.

The director of the town's hospital has ordered patients to leave the facility, said Muhammed Ismail, a physician at the hospital. Zarqawi's fighters had taken control of the hospital, and the director feared it would come under U.S. attack, Ismail said.

In Tall Afar, U.S. and Iraqi soldiers entered the fourth day of an offensive against insurgents who have controlled large sections of the city for nearly a year. On Monday night, soldiers dropped leaflets from helicopters in the eastern neighborhood of Sarai, where commanders believe insurgents are entrenched, warning noncombatants to evacuate the area.

About 5,000 soldiers from the Army's 3rd Armored Reconnaissance Regiment and the Iraqi army's 3rd Division continued advancing toward Sarai from all directions, searching homes, confiscating weapons and interrogating residents.

Early Monday morning, six members of an elite U.S. special operations unit were wounded in what was to have been a raid on the home of a suspected insurgent leader, according to U.S. commanders. Members of the unit, which is charged with searching for high-level insurgents, and the Army in Tall Afar would not provide details.

Tall Afar, a city of more than 200,000 about 40 miles from the Syrian border, is considered a logistical hub for insurgents operating across the country.

A roadside bomb killed one soldier in the 3rd Armored Cavalry Regiment in Tall Afar on Monday, and two British troops were reported killed by another roadside bomb in southern Iraq.

In Baghdad, insurgents launched a dawn attack on the Interior Ministry, killing two police officers, officials said. Other political violence Monday in Baghdad killed at least 13 civilians, the Associated Press reported.

A roadside bomb and other attacks killed four oil workers associated with a northern oil company in Kirkuk. Insurgents have mounted frequent attacks to disrupt Iraq's oil exports.

Mortar fire hit a residential neighborhood in the central city of Baqubah, killing six civilians, said Ahmed Fouad, a hospital physician. Eight other civilians were killed by a car bomb in the western town of Hit, the AP said.

In ongoing political negotiations, President Jalal Talabani said in a statement that he and the other top Kurdish leader, Massoud Barzani, had agreed to changes in the draft constitution. The changes would ease concerns among Arab countries that the wording of the draft loosened Iraqi ties to the Arab world.

The language at issue describes Iraq as an Islamic -- but not Arab -- country, a concession to non-Arab Kurds, who form about 15 percent of the Iraqi population.

Finer reported from Tall Afar. Special correspondents Hassan Shammari in Baqubah and Omar Fekeiki in Baghdad contributed to this report.

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