An Iraqi engineer freed in a U.S. military operation said Thursday that foreign insurgents held him captive at a desert outpost, beat and tortured him with electric shocks, and fled only after American aircraft buzzed overhead.

The rescue came as other Marines took part in Operation New Market (search), in its second day Thursday in western Iraq's Anbar province. U.S. troops carried out door-to-door raids in this Euphrates River city and launched a twilight airstrike against an insurgent target.

At least 11 insurgents have been killed in the operation, including an Islamic cleric who was shooting an AK-47 at troops, the military said. One Marine died after being wounded during the offensive's opening hours early Wednesday.

The engineer said he was held in the town of Obeidi, 80 miles west of Haditha (search) near the Syrian border, and one captor spoke with what seemed to be a Sudanese accent.

"I was blindfolded all the time. Then I heard voices of men who told me they had heard about me and had come to rescue me," the man told The Associated Press, who said he feared retribution if his name was made public. "Here I am with the Marines and I thank them for all their efforts. They have treated me fine and fed me well."

The Iraqi government and U.S. officials have repeatedly said foreign fighters are slipping across the border with Syria (search) and carrying out the worst of the attacks that have killed at least 620 people in Iraq this month.

Haditha, 140 miles northwest of Baghdad, lies along a major highway between Baghdad and the Syrian border. The city has no functioning police force, but U.S. military officials say Iraqi troops are expected to arrive soon.

After thousand U.S. troops encircled and blockaded Haditha this week, military commanders felt confident enough Thursday to lift roadblocks and allow the 90,000 residents to move more freely on the wide, dust-blown streets.

People drove cars slowly through the city or lingered cautiously outside their homes, watching U.S. troops trudge by as helicopters hovered overhead.

Two large explosions rocked the city before sunset. The cause of the blasts was not known.

The explosions were followed by an even bigger blast caused by the U.S. airstrike, which sent a giant mushroom cloud of dust and smoke into the air. The strike was against insurgents, the military said.

Military commanders said they were surprised that there was little resistance in Haditha. Earlier this month, militants launched a well-coordinated attack from the city hospital, killing four American troops in an ambush.

"I think it (the operation) has been successful in that the level of the insurgency is smaller than what it was before," Lt. Col. Lionel Urquhart, commander of the 3rd Battalion, 25th Marine Regiment, told an Associated Press reporter embedded with the Marines.

"I believe some people have fled based on intelligence. We face less resistance than we had thought," he said, adding that 16 suspected insurgents have been detained so far.

The campaign highlighted the U.S. military's concern about insurgents in Sunni-dominated areas of Iraq, where large U.S. operations are required to secure populated areas. Earlier this month, American forces staged a similar operation near the Syrian border, killing at least 125 insurgents.