American troops stormed through the western Iraqi town of Sadah near the Syrian border early Saturday, battling foreign fighters loyal to al Qaeda, according to witnesses and the U.S. military.

A force of 1,000 Marines, soldiers and sailors took part in the assault, which the military dubbed "Operation Iron Fist." The military had no immediate information about any American casualties.

The operation aimed to "root out al Qaeda in Iraq terrorists operating in the area and to disrupt terrorist support systems in and around the city," according to the military. Al Qaeda in Iraq, a group led by Abu Musab Zarqawi, is responsible for the most violent and deadliest attacks of the insurgency that followed the U.S.-led invasion of Iraq in 2003.

The U.S. military also announced Saturday that two American soldiers had been killed in action. One soldier was killed in Baghdad by a roadside bomb and the other in Baiji by a land mine.

For several months, insurgents in Sadah, about seven miles from the Syrian border, have escalated their "intimidation and murder campaign" against residents and local government officials, the U.S. military said in a statement. That enabled the insurgents to travel more freely within the region.

After U.S. and Iraqi forces retook control of Fallujah in November, the border town of Qaim became the center for al Qaeda command and operations in the west. Since May, U.S. forces have mounted more than a half-dozen assaults in the border area, a critical point where supplies and fighters crossing from Syria then head to other insurgent hot spots, including Ramadi, Mosul, Tall Afar and Karabilah. Last month, U.S. commanders in Baghdad said they would be increasing troop strength in the far west.

Twelve civilians were killed in an airstrike in Sadah on Friday night, said Ali Rawi, a physician at the hospital in nearby Qaim. Among the dead were seven women and children, he added. The bombs hit four houses, witnesses said.

"Two more families were killed Saturday at 11 a.m. when they were fleeing the town, driving on a dusty road," Rawi said. An ambulance rushed to the area, but "the driver was shot by the U.S. forces and his assistant was wounded," the physician said. "This is the only ambulance we have, as the others were either stolen or destroyed by the American forces."

Rawi's account could not be independently verified.

Mahmoud Obaidi, the mayor of Sadah, said U.S. forces had dropped leaflets from helicopters asking citizens to report armed men.

Power and water were cut off in the town, and all roads leading to it were blocked. The town's bus station was jammed with residents trying to flee. Shukri Ahmed, a municipal employee, estimated that 70 percent of the residents had fled by Saturday morning, when U.S. forces charged into the city.

"We took our money and some of our jewelry, and now we escape as the Americans said that there are black days waiting for us," said Jawad Khattab, 55. "They want to avenge their dead."

Some residents objected to the checkpoints set up by Marines and Iraqi army units to search anyone leaving the town. "It is so insulting," said Nabeel Mohammed. "They even search the women like they search men. I hope the resistance rises and gives them a lesson for what they did to us."

Abdul Karim Hadeethi, a local religious leader, said the assault was brought on by Shiite Muslims who want to ensure that Sunni Muslims do not vote in the Oct. 15 national referendum on a new constitution. Many Sunni Arab groups have rejected the proposed constitution and urged followers to vote against it.

"These operations will be an obstacle in the way of going to the polling centers," Hadeethi said. The U.S. military said Saturday that in addition to trying to stem the flow of foreign fighters crossing the border, it wants to secure the area for voting.

As Iraqi and American officials predicted, insurgent attacks have increased in the weeks leading up to the vote. In two attacks this week, more than 100 people died in sectarian violence apparently aimed at Iraq's Shiite majority.

On Thursday night, 85 people died in the northern city of Balad when three bombs detonated in public places crowded with people buying groceries and preparing for the beginning of the two-day weekend. The next morning, a car bomb exploded in a crowded vegetable market in Hilla, killing 14 people, including women and children.

A leading Sunni group, the Iraqi Islamic Party, on Saturday called the bombings "sinful doings." The group pleaded for a halt to the fighting with the approach of Ramadan, the holiest month in the Islamic calendar, which begins within days.

The party called for all Iraqis "to respect God and stop fighting and appeal to forgiveness and solve their problems by word, not by weapons. Otherwise, chances are lessening and whoever plans, provokes or perpetrates the bloodshed is responsible."

In a telephone interview, Naseer Ani, who heads the political office of the party, said revenge killings are being committed under the banner of sectarian violence. "We had to repeat our position on these acts one more time," he said. "We reject all the violent operations, in all its kinds."

A statement by the National Council for Unity and Building of Iraq, headed by Ayham Samarraie, a former minister of electricity, said the attacks in Hilla and Balad "victimized dozens of innocent sons of our country."

It added, "These acts will do nothing but increase our unity and will add another spot of shame on the forehead of the terrorists."

In Kirkuk, 160 miles north of Baghdad, three Iraqi police officers were killed and four wounded when their convoy was ambushed. The attack, which occurred at 3 p.m. Saturday, set two police cars ablaze, said Col. Adil Zain Alabidin of the Kirkuk police.

Special correspondents Omar Fekeiki and Bassam Sebti contributed to this report.