In Afghanistan, a gunman in an Afghan police uniform has killed six U.S service members in eastern Afghanistan. NATO said that the man opened fire during a training mission in Pachir Wagam district, Nangarhar province. He was also killed in the incident. U.S officials later confirmed that all six were Americans but declined to give further details. The Taliban issued a statement saying it was responsible for the killings. Spokesman Zabiullah Mujahid said the gunman had joined the border police in order to kill foreign soldiers. The spokesman said he found this opportunity and he killed six invaders. NATO said the incident is being investigated.Taliban insurgents have previously dressed as police to carry out attacks. Two suicide bombers in police uniform killed 12 police officers in south-eastern Paktika province last weekend.