A US drone strike targeting a militant compound on Saturday killed at least four rebels in Pakistan's restive tribal region near the Afghan border, security officials said.
The strike took place in Degan area of North Waziristan, known as a bastion of Taliban and Al-Qaeda.
"US drones fired four missiles on a compound, killing four militants," a senior security official told AFP.
The official said several drones were flying in the area at the time of the attack.
Another security official confirmed the strike and casualties.
He said the area had been the target of US drone strikes in the past, which killed several foreign militants.
The district is a stronghold of the Hafiz Gul Bahadur militant group, he said, adding that militants from the Afghan Taliban allied Haqqani network also operate in Degan.
The Al-Qaeda-linked Haqqani network in North Waziristan, blamed for some of the deadliest attacks in Afghanistan, is one of the thorniest issues between Islamabad and Washington.
Washington has long demanded that Pakistan take action against the Haqqanis, whom the United States accused of attacking the US embassy in Kabul last September and acting like the "veritable arm" of Pakistani intelligence.
Pakistan has in turn demanded that Afghan and US forces do more to stop Pakistani Taliban crossing the border from Afghanistan to launch attacks on its forces.
There has been a dramatic increase in US drone strikes in Pakistan since May, when a NATO summit in Chicago failed to strike a deal to end a six-month blockade on convoys transporting supplies to coalition forces in Afghanistan.
Islamabad and Washington have been seeking to patch up their fractious relationship in recent months, with the supply route reopening, after a series of crises in 2011 saw ties between the "war on terror" allies plunge.
But attacks by unmanned US aircraft remain contentious -- they are deeply unpopular in Pakistan, which says they violate its sovereignty and fan anti-US sentiment, but American officials are said to believe they are too important to give up.
Washington considers Pakistan's semi-autonomous northwestern tribal belt as the main hub of Taliban and Al-Qaeda militants plotting attacks on the West and in Afghanistan.