Over 1,000 coalition troops are battling a "substantial force" of suspected al-Qaeda fighters in the mountains of eastern Afghanistan.
Brig Roger Lane said the troops were sent to eastern Paktia province after an Australian special forces patrol was fired on yesterday.
No coalition casualties were reported but some enemy fighters have been killed, the British brigadier said. Australian and US forces are also involved in the British-led mission, dubbed "Operation Condor".
He said the fighting was in a mountainous area at an altitude of 8,000 feet but declined to be more specific.