A US drone strike on a militant compound killed five insurgents in northwest Pakistan's lawless tribal region near the Afghan border, officials said.
"The drone fired two missiles on a house in Hassokhel town," 25 kilometres (16 miles) east of Miranshah, the main town in North Waziristan, a security official said.
"So far five bodies have been recovered from the compound, which is ringed by militants."
Two other officials confirmed early Thursday attack, saying the number of casualties may go up.
Washington considers Pakistan's semi-autonomous northwestern tribal belt the main hub of Taliban and Al-Qaeda militants plotting attacks on the West and in Afghanistan.
North Waziristan is a stronghold of the Haqqani network -- Afghan insurgents blamed for a series of spectacular attacks on Western targets in Kabul -- and Pakistani Taliban chief Hakimullah Mehsud.
Islamabad has been resisting US pressure to launch a sweeping offensive against militants in the area.
Thursday's drone strike came after one on Wednesday that killed four militants in the same region, and followed a summit of NATO alliance leaders in Chicago earlier this week.
Pakistan says the missile attacks are counter-productive, violate its sovereignty, kill civilians and fuel anti-US sentiment.
Residents and local officials said Thursday's strike also damaged a nearby mosque where three worshippers believed to be Central Asian nationals were wounded. There condition was serious, one source said.
A neighbour, Mohammad Rafiq, told AFP the missile attack triggered fire at the compound. The dead militants, wearing joggers, were exercising in the courtyard when the missiles landed.
It was the fourth US drone strike reported in Pakistan since parliament in March demanded an end to them.
Relations plunged into crisis after US air strikes killed 24 Pakistani soldiers on November 26, prompting Islamabad to shut its Afghan border to NATO supplies and evict US personnel from an airbase reportedly used as a hub for drones.
Despite Pakistani criticism US officials are believed to consider the drone attacks too useful to stop altogether. They have argued that drone strikes are a valuable weapon in the war against Al-Qaeda and other Islamist militants.
Pakistan signalled last week that it was prepared to end the NATO blockade, but hopes of clinching a deal appeared to break down over the cost of transit rights.
US President Barack Obama snubbed Pakistan at the NATO summit, only seeing President Asif Ali Zardari in passing and voicing frustration with Pakistan.
Islamabad has been incensed by Washington's refusal to apologise for the November air strikes and US officials have so far rejected Pakistani proposals to charge several thousand dollars for each alliance truck crossing the border.
The blockade has forced NATO to rely on longer more expensive 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.
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.