A U.S. special forces convoy was ambushed in eastern Afghanistan, and five of the assailants were killed in a subsequent gunfight and coalition air assault, an army spokesman said Thursday. No coalition forces were injured.

About 20 attackers fired on the convoy with small arms and machine guns Wednesday from ridges overlooking a road between the towns of Gardez and Khost, Col. Roger King said. Two attackers were captured and taken into custody for questioning, he said.

The fate of the other attackers was not immediately clear.

The U.S. special forces, who were accompanied by a few Afghan militiamen, called in F-16s and A-10 aircraft as support in a firefight that lasted several hours, King said. He said the planes dropped two 500-pound bombs on suspected enemy positions.

"The road that goes through the pass is a traditional ambush site," King said.

The area in eastern Afghanistan is one of the most active in the war on terror, with attacks on coalition bases and troops nearly a daily occurrence. Most attacks involve rockets fired on U.S. bases using crude timers, most of which miss their mark.

It was not immediately clear who carried out Wednesday's attack, but U.S. officials believe Al Qaeda, remnants of the ousted Taliban regime and loyalists of renegade rebel leader Gulbuddin Hekmatyar are active in the area.

The groups are believed to have joined forces to attack coalition forces and the U.S. backed government of President Hamid Karzai.

The group of attackers "was obviously hostile to the coalition because it was an easily recognizable convoy in that it had Humvees included," King said.

Twenty-three nations participate in the U.S.-led coalition fighting the war against terror in Afghanistan from headquarters at Bagram Air Base north of the capital, Kabul.