The military said Wednesday that U.S. airstrikes in Afghanistan on Aug. 22 killed 33 civilians, far more than it had acknowledged amid Afghan claims of 90 civilian deaths.

A statement released Wednesday by the commander of U.S. forces in the Middle East summarized the findings of an investigation. The statement from Lt. Gen. Martin Dempsey asserted that despite the civilian deaths, U.S. forces involved in the attack in western Herat province acted based on credible intelligence, in self-defense and in line with their rules of engagement.

"We are deeply saddened at the loss of innocent life in Azizabad," Dempsey said. He blamed the Taliban.

"We go to great lengths to avoid civilian casualties in Afghanistan in all our operations, but as we have seen all too often, this ruthless enemy routinely surround themselves with innocents," he said.

The attack was on a suspected Taliban compound. Dempsey says the investigation also found that 22 insurgents were killed. An initial U.S. investigation had found that up to 35 militants were killed.

The U.S. military originally said five to seven civilians had died. The Afghan government and the U.N. have said the civilian toll was 90.

The issue of civilian deaths has outraged Afghans and strained relations with foreign forces in Afghanistan to help fight the insurgency. Afghan President Hamid Karzai has warned U.S. and NATO for years that they must stop killing civilians on bombing runs against militants, saying the deaths undermine his government and the international mission.

On Sept. 2, less than two weeks after the raid in the village of Azizabad, NATO's commander in Afghanistan, Gen. David McKiernan, issued a revised order meant to govern the tactics and procedures followed by U.S. forces when engaging in air and ground fights against the insurgents.

Several days after that, McKiernan ordered a second U.S. investigation into the deaths because pictures and video images surfaced that appeared to show 30 to 40 victims, including at least 10 dead children, laid out in a village mosque.

Zemeri Bashary, Afghanistan's Interior Ministry spokesman, said Wednesday that he had not yet seen the new U.S. report, but that the Afghan government stood by its original findings.

A joint delegation of Afghan lawmakers and local officials investigated within days of the strike and concluded that around 90 Afghan civilians, including 60 children, were killed. That finding was backed by a preliminary U.N. report.

McKiernan has said there are not enough U.S. ground forces in Afghanistan, so the military is relying more heavily on air power — a greater risk in a conflict where insurgents don't wear uniforms and intentionally mix with the general population for protection.

In a trip to Afghanistan in mid-September, Defense Secretary Robert Gates offered the people of Afghanistan his "personal regrets" over the civilian deaths and said he would try to improve the accuracy of air operations.