The soldiers and militants fought for four hours in the Musa Qala district of volatile Helmand province late Wednesday, coalition spokesman Maj. Quentin Innis said. There were no British casualties.
"The patrol base was receiving small arms and rocket-propelled grenade fire and British forces responded with small arms and mortars," Innis said. "We estimate 12 militants were killed."
Taliban militants have stepped up attacks against Afghan and U.S.-led coalition forces the last several months, particularly in southern Afghanistan. In an effort to stamp out the insurgents, American-led forces are waging their largest offensive in Afghanistan since the Taliban regime's 2001 ouster.
Elsewhere in the same province, suspected Taliban militants ambushed Afghan police who were patrolling in the district of Nad Ali late Wednesday, police said.
The police returned fire, killing three militants, while one police officer was wounded in the clash, provincial police chief Ghulam Nabi Malakhail said.
One coalition soldier also was killed Wednesday and six were wounded in the desolate southern Afghan province.
Their nationalities were not immediately disclosed by officials. Large numbers of British and American forces operate in Helmand, a hotbed of insurgent activity.
Britain is deploying 3,300 troops into Helmand, a region where Taliban militants have been able to operate at will until now. British military commanders say they expect to face fierce fighting in the region, where two British soldiers were killed earlier this week.
One coalition soldier was killed Wednesday and three others wounded in Helmand when their vehicle struck a land mine believed to have been left behind from previous conflicts, the military said.
Coalition and Afghan troops also raided a compound in a village in southern Uruzgan province, killing 12 Taliban militants hiding there, the coalition said.
One coalition soldier was wounded and a vehicle damaged when Taliban forces attacked a convoy Wednesday in Helmand province, Innis said. Coalition aircraft fired on Taliban positions.
Another coalition vehicle was hit by a roadside bomb in the southern province of Zabul, slightly wounding two soldiers, Innis said.
In another attack Wednesday, two militants killed only themselves in a failed suicide car bombing on U.S. forces. A purported Taliban commander claimed responsibility for the suicide bombing.
Meanwhile, a NATO soldier shot at a bus that "appeared to be a threat" to his military convoy in eastern Kabul province, wounding a passenger, NATO spokesman Maj. Luke Knittig said.
The soldier fired a warning shot to make the driver stop before shooting at the bus, Knittig said. Coalition soldiers are on high alert for suicide bombings and ambushes in Afghanistan.
During a visit to Kabul on Wednesday, U.S. Secretary of State Condoleezza Rice acknowledged a rise in violence, but promised victory over resurgent Taliban fighters. Afghan officials believe Taliban fighters are trying to scare NATO forces ahead of large-scale deployments to the south soon.