A British soldier was killed by a suspected member of the Afghan National Army (ANA) in Afghanistan on Monday, 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.
Return fire then killed the gunman at the scene, a spokesman for the MoD added.
Major Laurence Roche, spokesman for Task Force Helmand, said: "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 family of the soldier, who was attached to 21 Engineer Regiment, have been informed and have requested a 24-hour period of grace before further details are released.
The insider attack takes to 439 the number of UK service members to have lost their lives since operations in Afghanistan began in October 2001.
The so-called "green-on-blue" attacks have caused the deaths of all six British soldiers who have died during the current tour, Herrick 17.
The attack came as Afghan president Hamid Karzai travelled to America to discuss security in his country with Barack Obama.
More than 60 troops from the force have died in such attacks, the Telegraph reports.
At least 54 international troops have died as a result of such attacks, where Afghans turn their weapons on their coalition colleagues.