At least four insurgents were killed in a US drone strike on a militant compound in a lawless tribal area in northwestern Pakistan on Wednesday, security officials said.
"The drone fired two missiles on a house in the Tabai area near Miranshah," the main town in North Waziristan, a security official said, adding four militants were killed.
A local administration official and another intelligence official confirmed the early morning strike and casualties.
Waziristan is the most notorious militant stronghold in Pakistan's semi-autonomous northwestern tribal belt. Washington considers it the main hub for Taliban and Al-Qaeda to plot attacks on the West and in Afghanistan.
The strike was the third since Pakistan's parliament in March approved new guidelines on relations with the United States, including a call for an end to drone strikes on Pakistani territory.
It also came a day after a NATO summit on Afghanistan concluded in Chicago.
Pakistan says the drone strikes are counter productive and undermine government efforts to separate tribes from the militants, violate Pakistan's sovereignty, kill civilians and fuel anti-US sentiment.
Washington and Islamabad are uneasy allies and are still taking steps to repair a serious crisis in relations over last year's covert American raid that killed Osama bin Laden and November US air strikes that killed 24 Pakistani soldiers.
In retaliation, a furious Islamabad closed the Pakistani-Afghan border to NATO supply trucks, ruling out the port of Karachi as a way to ship goods to the 130,000 US-led international troops fighting insurgents in Afghanistan.
The move has forced NATO to rely on longer, more expensive northern routes through Russia and Central Asia, even as it plans a large-scale withdrawal of combat troops and hardware from Afghanistan by the end of 2014.
Deadlock over the blockade distracted from the NATO summit, even though US and Pakistani leaders expressed optimism that a deal will soon be reached.
US officials have so far rejected Pakistani proposals to charge several thousand dollars for each alliance truck crossing the border, and Washington also refuses to issue an explicit apology for the November air raid.
The frequency of the drone strikes has diminished in recent months, but US officials are believed to consider them too useful to stop altogether.
US President Barack Obama in January confirmed for the first time that US drones target militants on Pakistani soil, but American officials do not discuss details of the covert programme.
According to an AFP tally, 45 US missile strikes were reported in Pakistan's tribal belt in 2009, the year Obama took office, 101 in 2010 and 64 in 2011.
The New America Foundation think tank in Washington says drone strikes have killed between 1,715 and 2,680 people in Pakistan in the past eight years.