The incident was the second suspected drone attack in the region in the last 12 hours.
Another US drone attack late on Thursday killed at least three fighters when two missiles hit their hideout.
Unmanned remote-controlled drones are often the weapon of choice for the United States as it targets the Taliban and al-Qaeda fighters in remote, rugged areas along Pakistan's border with Afghanistan.
The US military does not confirm unmanned drone attacks but its forces and the Central Intelligence Agency (CIA) in Afghanistan are the only agencies that use such aircraft in the region.
The use of so-called Unmanned Aerial Vehicles (UAVs), which allow the military to operate in highly dangerous areas, is expected to grow in the coming years with the US defence department expected to buy 700 drones next year alone.
But heavy civilian casualties in drone attacks has sparked public anger in Pakistan.