Pakistani officials say US drones have launched two attacks against alleged Taliban strongholds, killing at least 15 people.
The attacks, carried out 12 hours apart, struck west and east of Miranshah, the main town in North Waziristan, a tribal region near the border between Afghanistan and Pakistan.
The first attack took place on Thursday night and killed two people, while the second one, launched on Friday morning, left 13 suspected fighters dead, the officials said.
They did not say if the dead from Thursday's raid were also fighters.
Exact details surrounding the attacks remain unclear.
"US drones fired three missiles at a house used by militants around 7:30am (0230 GMT)," a senior Pakistani security official in the northwestern city of Peshawar told the AFP news agency on Friday.
Other intelligence officers told the Associated Press that six missiles were fired during the attack.
Security officials in Miranshah said at least three of the dead were "foreigners", a term Pakistani officials use to describe al-Qaeda-linked fighters.
However, Yousaf Khan, a government administrator in Miranshah, said the identities of the victims had not been confirmed.
It is unclear if any of the dead are senior leaders in al-Qaeda or other "high value" targets for US forces.
Mustafa al-Yazid, al-Qaeda's third-in-command, was killed in a similar drone attack in North Waziristan last month.
The US military does not, as a matter of policy, confirm drone attacks.
But the US army and the Central Intelligence Agency are the only forces in the region who have access to pilotless drones.
North Waziristan is known to house Taliban and al-Qaeda fighters as well as members of the Haqqani network, a powerful group known for staging attacks on foreign troops in Afghanistan.
Pakistan's government publicly opposes US drone attacks, which are deeply unpopular among average people in the country.
However, it is widely believed that the country's security forces provide intelligence assistance for at least some attacks.
More than 900 people, including many civilians, have been killed in nearly 100 drone raids in Pakistan since August 2008.
There have been at least 35 suspected drone attacks so far this year, a large increase over previous periods.
Philip Alston, the United Nations special rapporteur on extrajudicial executions, issued a report earlier this month which questioned the legality of CIA-directed drone attcks, calling them "a licence to kill without accountability".
Critics say drone attcks amount to extra-judicial killings and create a mentality of "video-game warfare" among operators, where civilian lives are not seriously valued.
Waziristan came under renewed scrutiny from US forces when Faisal Shahzad, a Pakistani-American charged over an attempted bombing in New York, allegedly told US interrogators that he trained the region.
The US has pressured Pakistan to launch a military offensive in North Waziristan as American officials believe the region is home to al-Qaeda's leadership.
The Pakistani army has said it does not have the resources to mount such a campaign.