Missiles fired from unmanned US aircraft killed at least four people in Pakistan on Wednesday, officials said, ending an eight-week pause.
Pakistani security and intelligence officials said the missiles hit a home on the outskirts of the town of Miranshah in North Waziristan, killing at least four people.
The strike was the first such attack since Nov. 17 and could deepen anti-US sentiment in Pakistan, which was already running high after a Nov. 26 cross-border Nato air attack that killed 24 Pakistani soldiers.
"I think we were expecting the drone strikes after a long break," said Amir Rana, director of the Pakistan Institute for Peace Studies. "There were even a few reports were coming from the last two, three days that they are going to be resumed."
The Nov. 26 air strike triggered a deep chill in already troubled US-Pakistan relations, prompting Pakistan to close off Nato supply routes into Afghanistan.
A source in Washington confirmed that a US-operated drone had been fired at a militant target in Pakistan on Wednesday. The source said no well-known militants were believed to have been targeted or wounded in the attack.
Drones armed with missiles have played a significant role in US counter-terrorism operations as the Obama administration winds down the war in Afghanistan and Washington's focus expands to militant havens in countries including Pakistan.
The United States vacated a remote air base, used to stage classified drone flights against militants, in Pakistan's southwestern Baluchistan province last month. Pakistan had asked US forces to leave the base after the November air strike.
The Obama administration contends that drone strikes have helped weaken the central leadership of al Qaeda and put associated militant groups on the defensive. Others said the lull since mid-November had allowed militants to regroup.
"The militants were quite happy with this lull and they were publicly operating in the region as they were no more worried for their lives," a security official in the region told Reuters.
Many militant groups operate in Pakistan's tribal areas.
US officials denied the drop-off in lethal drone attacks was part of a deliberate moratorium on such flights linked to the political and diplomatic uproar over the November air strike.
Officials maintained that lethal drone strikes were based on the availability of targeting intelligence and implied that such intelligence had been in short supply recently.
The latest drone strike in Miranshah appears to demonstrate that if there was any kind of moratorium on such attacks, it has now been lifted.