The death of a soldier from 28 Engineer Regiment in Helmand Province was described as a "tragic incident" by the Prime Minster's spokesman today.
He said David Cameron's thoughts are "very much with the family and friends of the soldier".
The man, who hasn't been named, was shot dead by a suspected member of the Afghan National Army yesterday at Patrol Base Hazrat in the Nahr-e Saraj district of Helmand Province.
His family has been told.
He was the latest victim of a "green-on-blue" attack - where Afghans turn their weapons on their coalition colleagues.
The spokesman dismissed suggestions that a change of tactics are needed, insisting measures were already in place to improve vetting and screening of Afghan security personnel.
Task Force Helmand: 'This is an extremely sad day'
It is my painful duty to report the death of a soldier from 28 Engineer Regiment, who was shot and killed by a suspected member of the Afghan National Army at a patrol base in the Nahr-e Saraj district of Helmand Province.
This is an extremely sad day for the Corps of Royal Engineers and everyone serving with Task Force Helmand. Our thoughts are with the soldier’s family and friends at this time.
The soldier’s family have been informed and they have requested a 24-hour period of grace before further details are released.
– Spokesman for Task Force Helmand, Major Laurence Roche
British soldier killed by suspected member of Afghan army
A British soldier from 28 Engineer Regiment, attached to 21 Engineer Regiment, was killed by a suspected member of the Afghan National Army (ANA) yesterday, the Ministry of Defence has said.
The suspected ANA member used small arms fire first on his colleagues, before turning his weapon on the International Security Assistance Force soldiers in Patrol Base Hazrat in the Nahr-e Saraj district of Helmand Province.