Islamabad, Pakistan (CNN) -- Militants in northwest Pakistan shot and killed four men they accused of spying for the United States, police told CNN.
The bullet-riddled bodies were found Saturday dumped along a road in North Waziristan, a district in Pakistan's tribal region along the Afghan border, said senior police official Sajid Mohmand.
A note attached to one of the bodies read, "This is the fate for whoever works for the US," Mohmand said.
North Waziristan is widely believed to be a safe haven for the Pakistani Taliban and al Qaeda-linked militants fueling the insurgency in Afghanistan.
The district has seen a sharp increase in aerial strikes by U.S. unmanned drones.
Analysts say the targets are often chosen based on information gathered from local residents.
Over the past two years, the Pakistani Taliban have killed dozens of men in the tribal region after accusing them of providing information to Pakistani security forces and U.S. troops operating across the border in Afghanistan.
Journalist Nasir Habib contributed to this report.