U.S. Special Forces killed the unidentified man after he pointed a rifle at them in Lwara village, coalition spokesman Colonel Roger King told reporters at the allied base in Bagram.
"As members of the unit approached him to determine what his purpose was, the man leveled an AK-47 at them. They opened fire, the man was killed," said King.
Four rockets were fired near coalition positions in Lwara village in southeastern Afghanistan on Friday, prompting U.S. air strikes. King said three people found carrying documents and weapons have since been picked up in the area for questioning to determine if they belong to al Qaeda or the Taliban.
About a hundred U.S. infantry soldiers were flown into the Jalalabad area near the border with Pakistan at the weekend to conduct search and destroy operations, during which they blew up several caves.
"There were no reports of enemy contact," King said. But the soldiers found four caves, which may have been used by the al Qaeda or Afghan Mujahideen fighting the Russians during their occupation of Afghanistan.
"One cave appeared to have been used as a hospital. As the soldiers departed the area, they sealed off four caves," he said.
The Taliban, ousted from power in December after a massive U.S. air campaign and opposition advances, and al Qaeda, blamed for the September 11 attacks on the United States, have not been seen in large numbers since March, when U.S.-led troops engaged several hundred in the last big battle of the Afghan war.
Military officials believe the militants have broken up into small bands in eastern Afghanistan and western Pakistan and are moving easily across the loosely-guarded border along old infiltration trails and mingling with the local people.
Military officials fear these remnants could try to stage attacks in the run-up to the Loya Jirga, a traditional assembly of tribal elders, that will choose the war-shattered country's new transitional administration.
In the southern city of Kandahar, a bomb exploded outside the palace of the provincial governor on Friday night, causing slight damage. A spokesman for the governor blamed the attack on remnants of the Taliban trying to disrupt the delegate selection process there for the Loya Jirga.
"Obviously, we want the Loya Jirga to be a successful operation because it goes towards self-determination of Afghanistan," King said.
The weeklong assembly is due to begin in Kabul from June 10.
Concerns have also grown in recent weeks that al Qaeda and Taliban fighters may take advantage of the military stand-off between India and Pakistan to sneak back across the rugged, porous and largely unpatrolled border back into Afghanistan.
Islamabad has said it is pulling some of its troops along the border with Afghanistan to reinforce the eastern frontier with India, where a million troops are poised for war in a crisis triggered by an attack on the Indian parliament in December.
But flushing out Islamic militants that may still be hiding out in Afghanistan has proven to be a difficult task, with the country full of armed men working for local warlords.
British Royal Marines, for instance, have yet to encounter any enemy fighters in their current operation, codenamed "Buzzard," in the mountains south and east of Khost near the Pakistani border, or in three previous missions since they were deployed in Afghanistan in April.
In other war-related developments: