Seven marines were killed and eight wounded when their convoy was attacked in the al-Saqlawiya area on Monday, a journalist based in Falluja told Aljazeera.
Three Iraqi national guardsmen also died during the attack.
"Two explosive devices detonated as a multi-vehicle convoy passed through the area," journalist Abu Bakr al-Dulaimi said, adding that two Humvees were destroyed in the blasts.
"More than 100 soldiers have taken up rooftop positions in nearby buildings," said al-Dulaimi. As helicopters flew overhead, US soldiers sealed off the site in al-Saqlawiya, which is about 15km from Falluja.
The mainly Sunni Muslim city of Falluja, about 65km west of Baghdad, has seen scores of dead and wounded in recent weeks, including many civilians, after repeated US air strikes and ground attacks.
The US military has said it is targeting hideouts of foreign fighters. Falluja residents have told Aljazeera there are no such fighters in the city.
The latest deaths follow those of two US soldiers killed in a mortar attack near Baghdad, the American military said in a statement. The attack left 16 others wounded.
Also on Monday, a natural gas pipeline in northern Iraq was attacked, an act that could affect power in several cities, a police officer said.
The oil industry has suffered
The pipeline connects the Janbur fields with the Baiji power station some 70km to the south, said Colonel Muhammad Ahmad from the Oil Protection Police.
The Janbur fields are 20km south of Kirkuk.
Firefighters were able to extinguish the fire about half an hour after it started, he said. He added that experts from the company would replace the damaged pipeline within a day.
The Baiji electricity station can generate up to 400 megawatts a day and supplies the northern cities of Mosul, Kirkuk and Tikrit, with power, Ahmad said.
Drone shot down
In a related incident, fighters shot down an unmanned aircraft in Falluja. The drone, used to survey the city where US forces have seldom tread since an April assault, was being paraded through the streets on a pick-up truck.
US marines confirmed a drone crashed in the area of Falluja, but said it did not know the reason why.
"An unmanned aerial vehicle crashed in the vicinity of Falluja earlier today. The loss of this UAV will not have a significant effect upon MNF-I operations or capabilities," said Marine spokesman Lieutenant-Colonel TV Johnson.
"We've been operating a pretty long stretch without losing a
vehicle. Several US aircraft have been shot down in the Falluja region, but none in recent months."