Militants in Pakistan attacked tankers bringing fuel to NATO and US forces in Afghanistan on Friday, killing four people and causing a massive nighttime blaze.
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 US-led operation in Afghanistan are trucked through Pakistan after arriving by sea in the port city of Karachi.
Islamist militants and criminals often attack the slow-moving convoys, but the vast majority get through unscathed.
Pakistan also allows the United States to fire missiles from unmanned drones at militants on its side of the Afghan border.
The latest such attacks on Thursday killed at least six people in the North Waziristan tribal region, Pakistani intelligence officials said on condition of anonymity because they were not allowed to brief the media.
They said two attacks on a house and a car occurred within minutes of each other. The identities of the victims were not released.
American officials do not publicly acknowledge the program or say who they are targeting.
Pakistani intelligence is believed to cooperate with the CIA in at least some of the attacks.
There were on average two attacks a week last year, the most intense period of strikes since the program began in earnest in 2008.
Most of the strikes hit North Waziristan, one of seven tribal regions in the border area and the only one where the Pakistani army has not launched any operations.