Unknown armed men attacked tankers bringing fuel to NATO and U.S. forces in Afghanistan on Friday, killing four people and causing a massive nighttime blaze near Peshawar.

A group of around 15 militants armed with rockets and guns stormed a roadside terminal on the outskirts of the northwestern city of Peshawar. At least 12 tankers were set ablaze in the attack, said police officer Liaquat Ali Khan.

The dead men were drivers or their assistants, he said.

Much of the non-lethal supplies for the U.S.-led operation in Afghanistan are trucked through Pakistan after arriving by sea in the port city of Karachi. Militants often attack the slow-moving convoys, but the vast majority get through unscathed.