Two troops have been killed in southern Afghanistan by a gunman wearing an Afghan army uniform, NATO has said. The shootings took place at an international military base in Lashkar Gah, Helmand province, on Monday. NATO said the attacker was shot dead by International Security Assistance Force (ISAF) soldiers. The troops were later identified as a British soldier and a British marine. The incident comes after 17 Afghan civilians were killed in an attack for which a US soldier has been charged. An official in the Afghan defence ministry told the British Broadcasting Corporation (BBC) that the gunman was an Afghan soldier. A spokesman for the governor of Helmand said the shooting followed a \"verbal clash\" between Afghan and Nato soldiers, and that the Afghan involved was from Kunar province. Lt Col Jimmie Cummings, the ISAF spokesperson in Kabul, told the BBC: \"An individual wearing an Afghan national army uniform turned his weapon against ISAF force service members in southern Afghanistan today, killing two of our service members. \"The individual who opened fire was killed when coalition forces returned fire, and right now a joint Afghan and ISAF team are investigating this.\" The Taliban have claimed that the gunman was \"their man\". The attack appears to be the latest in a number of \"green on blue\" incidents - where members of the Afghan security forces turn their weapons on their international colleagues or trainers. The number of these incidents has risen since the inadvertent burning of Qur\'ans at a US base in February. Tensions were inflamed further by the killing of 17 Afghan civilians earlier this month. US Staff Sgt Robert Bales, 38, has been charged with killing nine Afghan children and eight adults in their homes in Kandahar province on March 11. He could face the death penalty if convicted. The case has undermined US relations with Kabul and led to calls for NATO to speed up its planned withdrawal of troops from Afghanistan. Sgt Bales\' trial could take years, contrasting with Afghan demands for swift and decisive justice. The Taliban called off peace talks in the wake of the deadly rampage.