The clash occurred opposite Pakistan's North Waziristan province, where Pakistan government forces have been attacking suspected al-Qaida positions intermittently for months.
"Several anti-coalition militants were killed and two members of the Khost provincial forces were injured in a firefight last night in Khost province," the US military said.
An Afghan security officer said three Taliban fighters were killed and one captured while two of his own men were wounded in the fighting in Gurboz district, 175 km southeast of Kabul.
In a conflicting statement, a Taliban spokesman said five government troops were killed and three of their fighters were wounded.
In a separate attack, rockets were fired into in the eastern city of Jalalabad on Friday and an Afghan woman and child were slightly wounded.
Some 18,000 US-led troops are still in Afghanistan after the US invaded that country in October 2001.