NAWA, Afghanistan — U.S. Marines moved into villages in Taliban strongholds in southern Afghanistan on Friday, meeting little resistance as they tried to win over local chiefs on the second day of the biggest American military operation here since the fall of the Taliban government in 2001.

One Marine was killed and several others wounded on Thursday, when some 4,000 Marines launched the operation in Helmand province — a remote area that is at the center of the country's illegal opium cultivation, which helps finance the insurgency.

So far, however, there has been little resistance from the Taliban, according to a military spokesman Capt. Bill Pelletier.

In the east, meanwhile, U.S. troops and personnel continued looking for an American soldier believed captured by insurgents on Tuesday, said Navy Chief Petty Officer Brian Naranjo, a U.S. military spokesman.

U.S. troops were brought in from nearby areas to help with the search, which included helicopters and Afghan Army support, officials said Thursday.

Britain's Defense Ministry said a roadside bomb Wednesday in Helmand killed two soldiers, including the most senior U.K. officer to have died in combat in Afghanistan. Lt. Col. Rupert Thorneloe was the commanding officer of the 1st Battalion Welsh Guards.

British Prime Minister Gordon Brown praised Thorneloe as someone "I admire and someone who will be missed by all his colleagues in the armed forces for the leadership he gave, the bravery he showed and the professionalism at all times he exhibited."

The aim of the operation in Helmand is not simply to kill Taliban fighters but to win over the local population, Pelletier said — a difficult task in a region where foreigners are viewed with suspicion.