| MIRANSHAH, Pakistan
MIRANSHAH, Pakistan A suspected U.S. drone aircraft fired two missiles into Pakistan's North Waziristan region on the Afghan border on Tuesday, killing six militants, Pakistani intelligence officials said.
The United States has stepped up its attacks by pilotless drones in Pakistan since a suicide bomber killed seven Central Intelligence Agency (CIA) operatives at a U.S. base in eastern Afghanistan on December 30.
The drone strikes are a source of friction between the United States and its ally Pakistan, which says they are a violation of its sovereignty.
U.S. officials say the missile strikes are carried out under an agreement with Islamabad that allows Pakistani leaders to decry the attacks in public. Islamabad denies this.
The latest drone strike targeted a house in a village in the Datta Khel district, 35 km (20 miles) west of Miranshah, the main town in North Waziristan, a region known as a hotbed of Taliban and al Qaeda militants.
"One missile hit a compound and the other hit a vehicle outside it. Six militants were killed," one of the Pakistani officials said. The death toll had initially been put at three.
Last Thursday, a U.S. drone targeted Pakistani Taliban leader Hakimullah Mehsud in the South Waziristan region on the Afghan border but it was known if he was among 12 militants killed.
The Pakistani Taliban, who are fighting the Islamabad government, later issued an audio tape purportedly from Mehsud, denying he had been killed.
Mehsud appeared in a farewell video sitting beside the bomber, a double agent, who killed the seven CIA operatives. The video was released 10 days after the brazen strike.
The video created the impression his Taliban movement had helped organize the attack.
Most of the recent U.S. missile strikes have been in North Waziristan, opposite the eastern Afghan province where the CIA were attacked, and a bastion of an al Qaeda-linked Afghan Taliban faction known as the Haqqani network.
The faction launches attacks into Afghanistan but is not fighting Pakistani security forces.
Pakistan has been resisting U.S. pressure to attack the Haqqani network, saying it has its hands full with an offensive in South Waziristan against the Pakistani Taliban, who have stepped up bomb attacks in towns and cities in response.
The military said soldiers killed 10 militants in the latest clash in South Waziristan.
Analysts say Pakistan has been reluctant to help battle Afghan Taliban factions based on its side of the border, in part because it sees them as potential allies in its 60 years of hostility with India, which is a close ally of the U.S.-backed government in Kabul.
(Writing by Augustine Anthony; Editing by Robert Birsel and Paul Tait)