Official: Afghan gunmen kill 2 U.S. troops (CBS/AP) KABUL, Afghanistan - NATO says two service members were shot dead in southern Afghanistan when two men, one of whom was believed to be an Afghan soldier, turned their weapons against international troops. An Afghan official confirms to CBS News that the dead were U.S. troops. Thursday's shooting is the latest case of Afghan policemen or soldiers - or militants disguised in their uniforms - killing NATO troops. Six NATO service members have been killed this way in less than two weeks. NATO says one of the gunmen was wearing civilian clothing and the other was believed to be a member of the Afghan army. Afghan violence not likely to change plans for U.S. drawdown U.S.: Military committed to Afghan mission Complete coverage: Afghanistan, 10 years later Two U.S. military advisers were shot and killed Feb. 25 inside their office at the Afghan Interior Ministry. Days before that, an Afghan solider shot and killed two other U.S. troops during a protest over the burning of Korans at a U.S. base. Six Americans have now been killed and at least 15 wounded in attacks in Afghanistan since the Islamic holy books were burned at a U.S. base there. "Clearly it's been a bad week," Crocker told CBS News, "but I'm quite confident we'll get through this.