Government administrator Akbar Khan said the guards were killed on Friday in the town of Landi Kotal, close to the Pakistan-Afghanistan border. He says the attackers slit the guards’ throats.
Militants also torched three vehicles, DawnNews reported.
Taliban militants often attack Nato supply trucks in Pakistan, though the vast majority of the goods are untouched.
Much of the non-lethal supplies for the war effort in Afghanistan come via Pakistan after being unloaded at the Arabian Sea port of Karachi in the south.