MARJAH, Afghanistan - About two dozen U.S. Marines were dropped from helicopters into Taliban-controlled areas of Marjah before dawn on Friday.
U.S. commanders are hoping the elite commandos will be able to locate and neutralize Taliban sharpshooters who have been targeting allied forces in the first seven days of the operation - the largest since the 2001-U.S.-led invasion of Afghanistan.
Meanwhile, Marines and Afghan troops are combing the countryside for insurgents as they march southward.
Local residents reported that some of the Taliban insurgents in the area are non-Afghan.
On Thursday, six coalition troops were killed in the fighting, bringing the death toll to 11 NATO troops. One Afghan soldier and two British soldiers were among Thursday's casualties.
According to U.S. officers, who spoke on condition of anonymity, some 120 Taliban have been killed in the first seven days of the incursion, but the remaining insurgents are still well entrenched in the area.
One British general said it would likely take another month to root out the Taliban and secure the area.
As soon as allied forces achieve their goal, the Afghan civil administration plans to rebuild the infrastructure quickly to win back the confidence of the local population, thereby helping to prevent the Taliban from entrenching itself again.
AP contributed to this report.