Two British servicemen have been shot dead by members of the Afghan Police Force, the Ministry of Defence has said.
A soldier from 1st Battalion Welsh Guards and an airman from the Royal Air Force were killed yesterday in the Lashkar Gah district of Helmand province, Afghanistan.
Serving as part of part of an advisory team, the two troops were providing security for a meeting with local officials at a patrol base, the MoD said.
Their families have been informed.
The attack was carried out by two people wearing Afghan Police uniforms, an International Security Assistance Force (Isaf) spokesman said.
One is on the run and the other was killed when forces returned fire, the spokesman added.
Shadow Defence Secretary Jim Murphy MP told Sky News' Murnaghan programme: "There's been a real emergence of these kind of attacks by people in what appear to be allied uniforms."
Major Ian Lawrence, spokesman for Task Force Helmand, said: "Sadly, it is my duty to confirm that a soldier serving with 1st Battalion Welsh Guards and an airman from The Royal Air Force have been shot and killed in the Lashkar Gah district of Helmand province.
"The thoughts and condolences of everyone serving in the Task Force are with their families and friends."
Since operations in Afghanistan began in October 2001, 374 members of UK forces have been killed in action in Afghanistan - bringing the total to 414 including accidents and illness.
The attack is the 16th incident this year in which Afghan soldiers or insurgents disguised in military uniforms have turned their weapons on foreign troops, according to Nato.
On Friday, a man wearing an Afghan army uniform shot dead a US soldier in eastern Afghanistan.
In March, Sergeant Luke Taylor, of the Royal Marines, and Lance Corporal Michael Foley, of the Adjutant General's Corps were shot dead by an Afghan soldier at the entrance to the UK headquarters in Helmand.
Five British soldiers were killed by a rogue Afghan policeman in November 2009. The gunman opened fire on the men in a military compound in Nad e Ali before fleeing. The Taliban later claimed responsibility.
Isaf has taken several security measures in response to the shootings, including assigning "guardian angels" - soldiers who watch over their comrades as they sleep.
Around 130,000 Coalition troops are fighting alongside some 350,000 Afghan security personnel against the Taliban-led insurgency but they are due to pull out of the country in 2014.
Mr Murphy added that there is "no realistic outlook for delaying the withdrawal".