AlQa'dah 11, 1436, Aug 26, 2015, SPA -- Two men wearing Afghan security force uniforms opened fire Wednesday inside a military base in southern Afghanistan, killing two NATO service members before being shot dead themselves, AP cited the international force as saying. NATO offered few details about the shooting in Afghanistan's southern Helmand province, which appeared to be the latest so-called "insider attack" to target foreign troops or contractors in the country. Afghan officials said they had no immediate details about the attack. In a statement, NATO said the two men in Afghan uniforms opened fire on a vehicle with international troops inside it. Both shooters were killed when NATO forces returned fire, it said. The motive for the attack was not immediately known and no group claimed responsibility for the assault.