Two British servicemen have been shot dead by members of the Afghan Police Force, the Ministry of Defence said.
A Royal Air Force airman and a soldier from 1st Battalion Welsh Guards were killed on Saturday in the Lashkar Gah district of Helmand province.
They were providing security for a meeting with local officials at a patrol base, the MoD said. Next of kin have been informed.
An International Security Assistance Force (ISAF) spokesman said the attack was conducted by two people wearing Afghan Police uniforms.
One is on the run and the other was killed when forces returned fire, the spokesman said.
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."