Suspected US missiles slammed into two Pakistani villages close to the Afghan border, killing 27 people including an Arab al-Qaeda operative and other foreign militants, intelligence officials said.
The al-Qaeda member was identified as Abu Kasha Iraqi, the officials said.
He had been living in Pakistan's tribal region for about three years, from where he had been organizing attacks on foreign forces in neighbouring Afghanistan, they said on condition of anonymity because they were not authorised to speak to the media.
Suspected US unmanned planes have fired at alleged militant targets in Pakistan at least 17 times since mid-August, putting pressure on extremists accused of planning attacks in Afghanistan and Pakistan - and perhaps terror strikes in the West.
But the marked uptick in their frequency is straining America's seven-year alliance with Pakistan, where rising violence is exacerbating economic problems gnawing at the nuclear-armed country's stability.
Scores of foreign al-Qaeda members are believed to be hiding out in the lawless border area, which is considered a likely hiding place for Osama bin Laden.
The United States rarely confirms or denies firing the missiles and the identities of those killed are only occasionally made public. Locals frequently say civilians, sometimes women and children, are among the dead.
The first attack took place in Mir Ali village in North Waziristan after drones had been flying overhead for several hours, the intelligence officials said, citing reports from agents and informers in the area.
The drones fired twice, hitting a house frequented by Abu Kasha Iraqi and a nearby car, killing 20 people, the officials said, citing reports from agents and informers in the field.
Around two hours later, a second set of missiles hit a village in South Waziristan, killing seven people, including an unspecified number of foreign fighters, the officials said.