The U.S. military is investigating civilian deaths in Afghanistan for the second time this week following Thursday air strikes that may have left seven non-combatants and 13 insurgents dead.

The casualties occurred after a convoy of Afghan and coalition troops came under fire during an ambush in the Ghormach district of Badghis province in the northern part of the country, said Col. Greg Julian, the public affairs officer for U.S. forces in Afghanistan.

The troops then returned fire and called in air support, and as a result there "may have been civilian casualties."

"If we find that innocent people were killed in this incident, we apologize and express our sincere condolences to the families and the people of Afghanistan," Julian said.

Two women and two children were among the seven civilians killed in the attack, said Badhgis deputy governor Abdul Ghani Saburi.

The attack Thursday comes just a day after Afghan President Hamid Karzai issued a plea to U.S. president-elect Barack Obama urging him to prevent undue loss of Afghan civilian life during U.S. military operations.

Monday air strike allegedly kills dozens

On Monday a coalition air strike in the Shah Wali Kot district in Kandahar province killed at least 23 children and 10 women who were attending a wedding, according to villagers.

Villager Abdul Jalil, a 37-year-old grape farmer whose niece was getting married, told an Associated Press reporter at the scene of the bombing that U.S. troops and Taliban fighters had been fighting less than a kilometre from his home.

Fighter aircraft destroyed his compound and killed 37 people, Jalil said. Karzai's office said the attack killed about 40 people and wounded 28.

Those deaths are being investigated by the U.S. military and the Afghanistan government.

In response, the U.S. military said in a Thursday statement that "several" insurgents were killed after an attack on a coalition patrol moving through the Shah Wali Kot region of Kandahar province between Monday and Wednesday.

Several civilians were attempting to flee the area at the time of the attack, said the U.S. statement, but the insurgents prevented them from leaving.

While the military did not say where they received this information, they quoted the Kandahar police chief as saying several civilians were wounded as they were trying to leave the area where the fighting took place.

The U.S. did not explicitly take responsibility for the alleged civilian deaths.

Between January and August, over two thirds of the 577 civilians killed by U.S.-led forces or the Afghan army have been killed in air strikes, the UN estimates.

Over the same period in the previous year, 477 civilians were killed by pro-government forces, according to the UN.

With files from the Associated Press