KABUL, AFGHANISTAN - Afghan officials said fighter aircraft battling militants accidentally killed up to 27 Afghans walking to a wedding ceremony in eastern Afghanistan early Sunday, the second military attack in three days with reports of civilian deaths.

The U.S. military blamed the claims on militant propaganda and said its missiles struck only insurgents.

President Hamid Karzai had already ordered an investigation into allegations that missiles from U.S. helicopters struck civilians Friday in eastern Afghanistan, though the Defense Ministry said Sunday that attack on the Nuristan-Kunar border killed or wounded 20 militants.

U.S. Army Gen. David D. McKiernan, the commander of NATO forces in Afghanistan, told The Associated Press on Sunday that the two incidents were being investigated. He noted that militants hide among and intimidate civilians.

U.S. spokesman 1st Lt. Nathan Perry said the military has repeatedly seen militants falsely claim civilians were killed.

"Whenever we do an airstrike, the first thing they're going to cry is 'Airstrike killed civilians' when the missile actually struck militant extremists we were targeting in the first place," Perry said. "At this time we don't believe we've harmed anyone except for the combatants."

In a statement, Karzai cited allegations by Tamim Nuristani, the governor of Nuristan province, that 15 civilians were killed and seven wounded in the Friday attack. During a Cabinet meeting Sunday, top Afghan officials prayed for any innocent lives lost, a presidential palace statement said.

"The killing and wounding of our countrymen as the result of airstrikes is news that always makes us sad," Karzai said.