Taliban fighters wore US Army uniforms in attack on Prince Harry's base The insurgents, organized into three teams, penetrated at one point of the perimeter fence. The insurgents appeared to be well equipped, trained and rehearsed," it said. Dressed in United States army uniforms and some in suicide vests, they attacked aircraft on the airfield with automatic rifles and rocket-propelled grenade launchers. Six US AV-8B Harrier jets were destroyed, each one estimated to cost at least £20 million ($30 million), and two were significantly damaged. Three refuelling stations were also destroyed and six soft-skin aircraft hangars were damaged, the coalition said. British troops from 5 RAF Force Protection Wing (51 Squadron RAF), the RAF Regiment, were first on the scene and fighting alongside US marines, repelled the insurgents in a gun battle lasting more than five hours. Two US Marines died in the attack and several British airmen were wounded, but none of the injuries were classed as serious. In all, eight servicemen and a civilian contractor were injured. A total of 14 attackers were killed and one was captured wounded. Hours after the attack, two soldiers from 3rd Battalion The Yorkshire Regiment, were killed at a checkpoint in the south of Nahr-e Saraj district by a member of the Afghan Local Police. The attacker is understood to have been returning from a joint operation when he turned his gun on them before he was himself shot dead. Three others were wounded. Four more troops died in a separate attack "suspected to involve members of the Afghan police" elsewhere in southern Afghanistan, though the coalition did not immediately reveal their nationality. Attacks by Afghan policemen or soldiers have killed at least 51 Nato troops this year, accounting for nearly one-in-six of all coalition deaths. Instances of Afghan soldiers or policemen firing on comrades within their own ranks are also widespread. Coalition commanders have struggled to understand the motivation for the attacks because few of the assassins are captured alive. Weak vetting of new recruits has been blamed, but few of the attacks are thought to be due to direct infiltration by the Taliban. An analysis of 34 such attacks in 2012 found only one was caused by direct infiltration, two were due to personal grievances flaring up into violence and two were due to an Afghan being coerced into attacking, perhaps because of threats against his family. The motivation in 24 remained a mystery, though commanders believe they are often caused by arguments rooted in cultural clashes. The Afghan forces have announced they will re-vet tens of thousands of troops to look for hints of extremism or links to the insurgency. Hundreds have already been kicked out. Counter intelligence officers have also been embedded in Afghan units to look out for potential assassins. Nato troops have been told to be on alert and armed sentries, known as guardian angels, are deployed to watch for attacks whenever they interact with Afghan forces. American special forces troops announced they would halt training recruits to the Afghan Local Police programme, where men are paid and trained to protect their own villages, until members had been re-vetted.