Afghan President Hamid Karzai on Monday condemned the U.S. coalition's killing of 14 "private security guards" in eastern Afghanistan, saying such attacks will only "expand the gap" between the people and his government, as well as its western backers.

In a statement, the president said that those killed in the eastern Khost province on Sunday were working for a road construction company.

"Despite the Afghan government's constant requests to NATO and coalition forces to prevent air strikes that cause the death of innocent people and civilians, such an incident has happened once again which has no justification," Karzai was quoted in the statement as saying.

But the U.S. coalition and Karzai's own Interior Ministry said in a joint statement that U.S. troops shot at three vehicles carrying armed men only after those in the vehicles opened fire on their forces.

"The occupants of the vehicles got out of their vehicles and fired on the coalition forces who returned fire with rifles and helicopter gun fire," the joint statement said.

"There were secondary explosions in the vehicles, and 14 armed men were killed. Numerous ammunition belts and small-arms weapons were recovered from the vehicles."

The military said it has launched a joint investigation with Afghan authorities into the incident.

Karzai has been increasingly vocal in his condemnation of U.S. and NATO tactics after a recent spate of incidents involving U.S. coalition troops in which Afghan civilians were killed. Last week, Karzai appealed to U.S. president-elect Barack Obama to ensure that Afghan civilians are not killed in coalition operations.

Last week, the U.S. said a joint U.S.-Afghan investigation found that 37 civilians and 26 militants were killed during a battle between U.S. troops and Taliban militants in the village of Wech Baghtu in the southern Kandahar province. The U.S. has said the militants forced the Afghan villagers to stay in Wech Baghtu during the battle.

With files from the Associated Press