Bagram, Afghanistan ? A U.S. special forces soldier was killed while on patrol in eastern Afghanistan on Sunday when his unit came under heavy fire, a U.S. military spokesman said.

There were no other reports of coalition casualties in the firefight, which started when suspected al-Qaida or Taliban forces engaged U.S. forces with at least small-arms fire at approximately 5 p.m. local time, said Capt. Steven O’Connor, a U.S. military spokesman at Bagram air base.

Sgt. Arden Vance Jr., 38, of Morgantown, W.Va., was in the 19th Special Forces Unit of the West Virginia National Guard. He had been in the National Guard for 10 years, spokesman Maj. Mike Cadle said.

It was unclear whether there were any casualties on the opposing side.

Small teams of U.S. special forces and other coalition soldiers are operating throughout eastern Afghanistan, conducting search operations for Taliban and al-Qaida members.

Some 1,000 British-led troops launched the sweep through mountains near the city of Khost on Friday, saying they believed a “significant number” of fighters were there after an Australian patrol was attacked the day before.

The Australians came under heavy fire there for five hours, until calling in strikes by American A130 gunships, which killed 10 people who the coalition said were Taliban and al-Qaida fighters.

Lt. Col. Ben Curry, a British military spokesman, said Sunday that coalition troops had searched half the area targeted by the sweep, named Operation Condor, but encountered no opposition fighters. A small amount of ammunition was found, including two 120 mm rockets and a few cases of 12.7 mm ammunition, Curry said at Bagram base north of Kabul.

An Afghan tribe whose fighters were killed in Thursday’s A130 strike disputed the coalition account of the fighting there. A delegation from the tribe discussed the bombing with U.S. officers Saturday at Khost airport, where American special forces are based.

Members of the Sabari tribe said their fighters were skirmishing with the Balkhiel tribe in a dispute over a stand of trees near their villages 30 miles north of Khost when the bombs fell. Sabari elders denied firing on the Australians or the U.S. aircraft or having links to al-Qaida or the deposed Taliban militia.

However, a U.S. military spokesman, Maj. Bryan Hilferty, said Sunday he had “no reason to believe” the tribe’s account. “They were shooting heavy machine gun and mortars at us. That is known al-Qaida and Taliban area,” he said.

Coalition forces had observed the area for several days and believed it was being used as a transit point by al-Qaida and Taliban members, Hilferty said.

British forces said three more soldiers suffering from the “winter vomiting” bug officially known as Norwalk-like virus after the Ohio town where it was first identified would be evacuated to Britain Sunday.

Eight others already have been evacuated seven to Britain and one to a U.S. military hospital in Germany. Some 333 British troops were under quarantine, but that was lifted Sunday after the military said no more cases were found in the past 48 hours. British defense officials in London identified the illness Saturday.