At least 12 people, most of them Arabs, were killed when a missile struck a house early Thursday in a Pakistani tribal region known as a safe haven for Al Qaeda militants, officials and residents said.
Residents in Azam Warsak village in South Waziristan told AFP that the home was destroyed by a missile fired from a pilotless drone and the loud blast was heard miles (kilometres) away in the rugged valley.
Security officials said they had received a report that a "guided missile" fired from neighbouring Afghanistan had hit a house belonging to a local tribesman.
"The death toll is now 12 to 13 people, three of the dead appear to be from Punjab (central Pakistani province where several militant groups are based) while the rest are Arabs," a security official told AFP.
At least five people were also injured in the attack, officials added.
There was no immediate confirmation from the military about the attack, but US military drones have carried out previous strikes targeted at key Al Qaeda figures active in the region.
Libyan militant and Osama bin Laden's operational number three Abu Laith Al Libi was killed in a missile strike on January 29 in the Pakistani tribal area of North Waziristan.
Al Qaeda number two Ayman Al Zawahiri vowed to avenge Al Libi's death in a videotape message broadcast on an Islamist website on Wednesday.
Pakistani officials do not confirm US strikes against Al Qaeda-linked militants on its territory because of sensitivities over sovereignty.
Previous US missile attacks have claimed the lives of several militants in Pakistan.
A US Predator targeted Al Zawahiri in January 2006, killing several rebels and civilians but missing him and sparking protests in Pakistan. (AFP)
Missile strike kills 12 in Pakistan tribal belt: officials