An armed man wearing an Afghan army uniform has shot and killed a member of the US-led multinational forces fighting in Afghanistan.
Sunday's incident was the latest in a spate of so-called insider attacks that are fracturing the trust between NATO and Afghan forces.
Separately, officials said 11 Afghan civilians were killed by land mines on Sunday in explosions in the east and south.
The UK defence ministry confirmed that the insider attack had claimed the life of a British soldier from The Royal Scots Borderers, 1st Battalion The Royal Regiment of Scotland.
It said the soldier was shot by an individual wearing an Afghan army uniform at his base in the Nad-e Ali district of the southern Helmand province.
The defence ministry did not name the soldier but said his next of kin have been informed.
Mohammad Zarak, spokesman for Helmand's governor, said the shooting took place in Nad-e Ali district after an argument between an Afghan soldier and coalition soldiers.
Coalition figures show at least 60 foreign soldiers have been killed so far this year and others have been wounded in about 45 insider attacks, where members of the Afghan security forces or fighters dressed in their uniforms turn their guns on US and allied troops.
The insider attacks have raised questions about how effectively the allied forces can train the Afghans to take over security of their own country in 2014 and beyond.
Foreign forces are due to turn over security responsibility to the local military by the end of 2014.
In other developments, a roadside bomb killed three men, two women and a baby in Khost province of eastern Afghanistan, Youqib Khan, deputy provincial police chief, said.
He said their vehicle hit the bomb as they were returning from a hospital.
Three other civilians were killed when their vehicle detonated a land mine on the road between Helmand and Kandahar provinces, a government statement said.
Also in the south, two civilians who were walking were killed by a land mine in Khakrez district of Kandahar, Ahmad Jawed Faisal, a spokesman for the provincial governor, said.
The UN says homemade bombs continue to be the weapons that kill the most civilians in the war.