The drone fired two missiles, destroying a vehicle and a compound near Miranshah town in North Waziristan tribal district, on the Afghan border.
The dead militants include some foreigners and are believed to be part of the Haqqani network, officials say.
The group is believed to be behind a number of attacks against US troops in Afghanistan.
North and South Waziristan are regularly targeted by drone missiles.
The US says the region provides sanctuary to al-Qaeda and Taliban insurgents who are involved in attacks on Nato forces in Afghanistan.
"The dead included local Taliban as well as some Arabs and Uzbek nationals," news agency Reuters quoted an unnamed intelligence official in North Waziristan as saying.
Initial reports said four to five militants were killed, but officials later said the toll had gone up after more bodies were pulled out from the rubble.
The attack on Wednesday morning was one of the biggest in recent weeks.
Last month, drone strikes killed at least 30 people in less than 24 hours in the area.
Drone attacks have escalated in the region since President Barack Obama took office in 2008. More than 100 raids were reported in the area last year.
The US does not routinely confirm drone operations, but analysts say only American forces have the capacity to deploy such aircraft in the region.
Pakistan publicly criticises drone attacks, saying they fuel support for militants. But observers say the authorities privately condone the strikes, although there have been recent signs that they want to limit the scope of such attacks.
A number of militants, some of them senior, have been killed in the raids, but many civilians have also died.
A US drone attack has killed at least 21 militants in north-western Pakistan, local intelligence officials said.