The U.S. military said five Marines and two Afghans were wounded in the clash, which an Afghan governor placed in Daychopan district of Zabul province, some 190 miles southwest of Kabul.
"The battle occurred as the Marines and Afghan fighting forces approached a site identified as a likely ambush site. As Marines advanced an intense firefight ensued," said Capt. Eric Dent, a U.S. Marine spokesman.
Dent said in an e-mailed statement that four enemy fighters were captured — two of them wounded in the battle — and several killed, but gave no exact death toll.
The five wounded Marines were in stable condition, he said. The injured Afghans were a soldier and an interpreter.
Jan Mohammed Khan, the governor of neighboring Uruzgan province said the convoy was ambushed by a group of more than 100 Taliban in a mountainous area called Sharaboz Kothal.
He said U.S. jets and warplanes joined the fray, scattering the insurgents.
"We collected 21 bodies," Khan told The Associated Press. "The rest ran back into the mountains."
Dent made no mention of air strikes.
Some 2,000 Marines based in Uruzgan have clashed repeatedly with large bands of militants in the mountainous area which also straddles Zabul and Kandahar provinces.
More than 40 have now been reported killed during the past week, in a rerun of fierce fighting last August and early September in the same area which left well over 100 Taliban and one American special operations soldier dead.
Khan said the dead included two local Taliban commanders, Mullah Jabar and Mullah Jalan.
About 450 people have died across Afghanistan this year in a wave of violence that has cast doubts on plans to hold national elections in September.