Suspected militants in Pakistan's Khyber tribal region on Monday attacked a NATO container truck and killed its two drivers, officials and locals said. The officials said dozens of suspected militants attacked the NATO truck in Jamrud area on a main highway connecting Pakistan and Afghanistan Monday morning. The officials and witnesses said two drivers and their cleaner were injured in attack. The two drivers later succumbed to wounds. Local residents said around 50 armed men fired at the NATO truck and later set it on fire. No group has claimed responsibility for the attack yet. Pakistan is a main supply route for NATO troops in Afghanistan and officials estimate nearly 70 percent of the supplies are transported for foreign troops through this shortest route. Taliban and another militant group in the tribal region, bordering Afghanistan, routinely launch attacks on NATO assets. Attacks on NATO trucks in Khyber region have increased in recent weeks. Last month, three separate attacks on NATO vehicles had left a man dead and three others injured. The surge in attacks came at a time when the NATO troops are devising exit strategy and the United States is using the Pakistani route to withdraw its heavy machinery.