Amid U.S. regret over civilian deaths in Afghanistan, the commander of U.S. forces there voiced doubts Wednesday about whether American bombing was to blame.

"We have some other information that leads us to distinctly different conclusions about the cause of the civilian casualties," Gen. David McKiernan said.

Speaking to reporters at Camp Eggers in Kabul, McKiernan said Taliban extremists beheaded three villagers over the weekend in the start of what he described as an extended battle that ended with U.S. airstrikes killing at least 25 Taliban militants.

McKiernan noted the claims of local officials that civilians were also killed.

He said a joint U.S.-Afghan investigation of the incident, which began Wednesday, would probably take a few more days.

"We do have people out there on the ground who will continue to follow this up with our Afghanistan counterparts to get to the truth," McKiernan said. He added: "It is certainly a technique of the Taliban and other insurgent groups to claim civilian casualties at every event, so we've just got to do the right investigation on this."

The International Committee of the Red Cross found that women and children were among the dead, but McKiernan cast doubt on whether they were killed by the airstrikes.

By McKiernan's account, the deadly weekend began with the beheadings that he called a possible trigger by the Taliban to ambush local police.

"The contact grew, the police asked for reinforcement from the Afghanistan army, and it eventually got to the point where the [province] governor asked for U.S. support in this contact," McKiernan said.

The U.S. airstrikes lasted for several hours, McKiernan said.

The deaths came just before the Afghan and Pakistani leaders arrived in Washington for meetings with President Barack Obama. At the same time, U.S. Defense Secretary Robert Gates arrived in Kabul on Wednesday for a two-day visit to Afghanistan to oversee troop and security conditions in the battle-torn nation.

McKiernan said he hopes the Washington meetings ultimately will create a "better security coordination, in my case, along the border between the two countries, and enhances the overall security conditions in the region."