Miranshah:
US missiles killed four militants in a Taliban stronghold of Pakistan on Wednesday, officials said, amid increasing strains with the West over a six-month blockade on NATO supplies into Afghanistan.
A drone targeted a compound near Miranshah, the main town of the tribal district where Pakistan has resisted US pressure to launch a sweeping offensive against militants fighting US troops in neighbouring Afghanistan.
"The drone fired two missiles on a house in the Tabai area near Miranshah," one of the security officials told AFP on condition of anonymity because he was not authorised to speak to the media, adding that four militants were killed.
"It is not immediately known if an important target is among those killed," he said.
The area 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 denies any support for Haqqani activities, but the former chief US military officer, Admiral Mike Mullen, called them a "veritable arm" of the Pakistan Inter-Services Intelligence agency.
US officials say its leaders are based in Waziristan, the most notorious militant stronghold in Pakistan's semi-autonomous northwestern tribal belt.
Washington considers the area the main hub of Taliban and Al-Qaeda plotting attacks on the West and in Afghanistan. US officials have accused Pakistani intelligence agents of playing a double game in supporting or at least turning a blind eye to Afghan insurgents.
A local administration official and another intelligence official confirmed Wednesday's drone strike and casualties.
Residents said the bodies had been charred badly and militants had cordoned off the area and were sifting through the rubble.
It was the third US drone strike reported in Pakistan since parliament in March demanded an end to the attacks on Pakistani territory, as part of new guidelines for Islamabad's often stormy relationship with Washington.
Relations plummeted into deep 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.
Pakistan says the missile attacks are counter productive, violate its sovereignty, kill civilians and fuel anti-US sentiment.
The frequency of the drone strikes has diminished since November, but US officials are believed to consider them 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 this week's NATO summit in Chicago, 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.