According to US military officials, the clash on Friday began when US forces opened fire on a group of 30 to 40 armed men.
"They were armed, they were acting in a hostile manner, so we fired on them and then we pursued them with the Afghan National Army," US military spokesman Lieutenant-Colonel
Bryan Hilferty told a news briefing.
"Nine of them were killed in that battle, and there were no coalition casualties."
At least 10 US snipers from a special operations task force in Afghanistan were involved in the battle, supported by a nearby battalion of Afghan troops. The rest of the group of suspected guerrillas reportedly fled.
The clash was one of the largest reported in recent months between 13,000 US-led troops in Afghanistan and their local allies and Islamic fighters from groups including the ousted Taliban and al-Qaida.
Suspected fighters captured
In a separate incident on Thursday, 14 suspected fighters were captured at a compound north of the eastern town of Khost.
Troops from the 1st Battalion, 501st Parachute Infantry Regiment launched an air assault and found 100 mortar rounds, 100 rocket propelled grenades, rifles and other ammunition at the compound.
"We had intelligence that led us to a compound north of Khost," Hilferty said, declining to comment further on the nature of the intelligence. The 14 suspects are being questioned.
The US military is hunting al-Qaida and Taliban fighters, mainly in the south and east of Afghanistan.
It has shifted away from large-scale operations to deploying smaller outfits into rural areas where they spend several days in each location to build relations with locals and improve intelligence gathering.
The prime targets are al-Qaida chief Usama bin Ladin, his deputy Ayman al-Zawahiri, Taliban supreme commander Mullah Muhammad Umar and renegade commander Gulb al-Din Hekmatyar.