The unmanned aircraft fired missiles in mountainous Spalga village, 15 kilometres (nine miles) northeast of Miranshah, the main town in North Waziristan tribal district and a stronghold of Taliban and Al-Qaeda-linked rebels.
"US drones fired six missiles targeting a militant vehicle and a nearby rebel compound owned by a Tehreek-e-Taliban Pakistan (TTP) leader, Rahimullah, killing six militants," a senior security official in Miranshah told AFP.
Five militants were also wounded in the attack, said the official, who spoke on condition of anonymity. The identities of those killed and injured were not immediately known.
Another security official also confirmed the strike and casualties but said it was not clear how many drones had taken part in the attack.
He added that several drones were still flying in the area.
Earlier in the day, a US missile strike in the lawless tribal region of South Waziristan had missed its target -- a militant vehicle -- allowing at least four militants to flee.
Missile attacks doubled in the tribal areas last year as the covert campaign was stepped up, with more than 100 drone strikes killing over 670 people in 2010 compared with 45 strikes that killed 420 in 2009, according to an AFP tally.
Most have been concentrated in North Waziristan, the most notorious Afghan Taliban and Al-Qaeda bastion in Pakistan, where the United States wants the Pakistan military to launch a ground offensive as soon as possible.
But despite pressure from Washington, Pakistan has stalled on launching such an offensive in North Waziristan, saying its troops are already overstretched.
The US ambassador to Islamabad, Cameron Munter, told reporters in December that US officials would like to see Pakistan launch an offensive there "tomorrow" but acknowledged that troops were stretched too thin to act immediately.
The United States does not confirm drone attacks, but its military and the Central Intelligence Agency (CIA) operating in Afghanistan are the only forces that deploy them in the region.
The US strikes are deeply unpopular among the Pakistani public, who also see military action on Pakistani soil as a breach of national sovereignty.
But Islamabad tacitly cooperates with the bombing campaign, which US officials say has severely weakened Al-Qaeda`s leadership and killed high-value targets including the former Pakistani Taliban chief Baitullah Mehsud.
US officials say Pakistan-based militants are active in escalating a nine-year insurgency in Afghanistan, putting up a deadly fight against 140,000 US-led NATO troops there and seeking to bring down the Western-backed government in Kabul. (*)
Editor: Kunto Wibisono
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