By Ashish Kumar Sen and Rowan Scarborough
Western nations preparing to withdraw from combat in Afghanistan increasingly are alarmed by Afghan security forces turning their weapons on allied troops, attacks that the Taliban claim as proof of their sway over local troops.
Five such attacks have occurred in the past week — the deadliest on Friday, when six U.S. troops were killed by Afghan security personnel in two separate incidents.
The so-called green-on-blue attacks have heightened tensions and frayed nerves among coalition troops as international forces aim to withdraw from Afghanistan by the end of 2014.
