Afghanistan's president has ordered an investigation into allegations that missiles from U.S. helicopters struck civilians, though the Ministry of Defense said Sunday that the attack killed or wounded 20 militants.

President Hamid Karzai ordered the defense and interior ministries, as well as local government officials, to investigate Friday's attack in eastern Afghanistan.

The issue of civilians casualties has caused friction between the Afghan government and U.S. and NATO troops in the past, and it has weakened the standing of the Western-backed Karzai in the eyes of the population.

Karzai has repeatedly called for better coordination between Afghan and foreign troops in pursuing militants through populated areas, and he has pleaded for international troops to cut down on civilian casualties. Deaths of ordinary Afghans caused a huge outcry in summer of 2007, but there have been fewer accusations of such killings in recent months.

Karzai's statement quoted allegations from Gov. Tamin Nuristani, the governor of Nuristan province, as saying that 15 civilians were killed and seven wounded.

However, the Ministry of Defense on Sunday said up to 20 militants were killed and wounded in an air attack in Kunar province Friday. The area of the attack is on the border between Kunar and Nuristan, and both statements referred to the same incident.

The U.S.-led coalition insists those killed were militants who had previously attacked a NATO base with mortars. Despite Nuristani's claims, a coalition statement said there are "no official reports of non-combatant injuries or casualties."

Meanwhile, the chief government official in the Deh Bala district of Nangarhar province said villagers reported that between 30 and 35 people walking in a group toward a wedding were killed in a bombing early Sunday. Up to 10 others were wounded, he said.

Haji Amishah Gul said the group was hit while resting in the shadow of a mountain. Those killed included men, women and children, he said.

No other officials could immediately confirm Gul's claim because of the remote location of the incident. No hospitals reported receiving any of the wounded.

The U.S.-led coalition said an airstrike killed several militants in Nangarhar. Spokesman 1st Lt. Nathan Perry said he had no reports that civilians were among those killed.

Karzai's statement appeared to indicate that Afghan civilians were fleeing in cars during the time of Friday's airstrike by coalition helicopters because of a warning from the U.S. coalition.

"Coalition forces are saying that this operation was against armed insurgents in the area, but Gov. Nuristani is insisting that three hours before this airstrike the people were informed by international forces that they should leave the area because of a possible airstrike against insurgents," the statement said.

Perry said Sunday that military reports still indicated that Friday's strike in Nuristan hit two vehicles carrying militants who had attacked a NATO base with mortars.

U.S. coalition reporting indicated that the Kunar and Nuristan incidents, reported by the Ministry of Defense and Nuristani respectively, were the same, he said.

Elsewhere, in the southern province of Helmand — the country's other hotly contested region — a clash killed seven Taliban and two police, said Helmand provincial police chief Mohammad Hussein Andiwal. Five other officers were wounded during the Saturday fight in Nawa district, he said.

The coalition said several militants were also killed Friday during an operation in Ghazni province.