A missile struck a house in a Pakistani region known as a safe haven for al Qaeda militants early on Thursday, killing at least eight people, residents and intelligence officials said.
The attack took place near Kaloosha village in the South Waziristan tribal region on the Afghan border.
"The blast shook the entire area, about eight people were killed," Behlool Khan, a resident of the area, told Reuters.
A security official said he believed the missile was fired by U.S. forces, who are operating in neighbouring Afghanistan.
U.S. forces have fired missiles at militants on the Pakistani side of the border several times in recent years, most recently in late January when one of Osama bin Laden's top lieutenants, Abu Laith al-Libi, was killed.
That missile was believed to have been fired by a U.S. pilotless drone.
However, neither U.S. nor Pakistani authorities officially confirm U.S. missile attacks on Pakistani territory, which would be an infringement of Pakistani sovereignty.
Pakistan, an important U.S. ally despite widespread public opposition to the U.S.-led campaign against al Qaeda and the Taliban, says foreign troops would never be allowed to operate on its territory.
Many al Qaeda members, including Uzbeks and Arabs, and Taliban militants took refuge in North and South Waziristan, as well as in other areas on the Pakistani side of the border after U.S.-led forces ousted the Taliban in Afghanistan in 2001.
From sanctuaries in the lawless border belt, the Taliban have orchestrated their insurgency against the Afghan government and the U.S. and NATO forces supporting it.
Increasingly, so-called Pakistani Taliban have been mounting attacks in Pakistani towns and cities, many aimed at security forces and other government targets.
