US drone attacks are being stepped up along the Afghan-Pakistan border
Two missile strikes by US drone aircraft have killed at least 12 suspected militants in north-west Pakistan, security officials say.
The attacks took place in the tribal area of North Waziristan.
The identities of those killed in the attack, the latest of more than a dozen this year, are not yet known.
North and South Waziristan are known to provide sanctuary for al-Qaeda and Taliban militants, who are often targeted by drones.
Locals say the attacks have destroyed many training camps and compounds. They have also killed dozens of local and foreign militants, officials say.
Wednesday's first strike took place at Mizar Madakhel village, some 50km (30 miles) west of Miranshah, the main town in North Waziristan. This was followed by a second attack in the same area.
The first attack targeted a vehicle and a compound which were being used by suspected militants, killing eight of them, reports say.
The second strike targeted two vehicles, which killed another four.
Correspondents say the United States has stepped up drone attacks in the region since seven CIA officers died in a suicide bomb attack at a US base across the border in Afghanistan last December.
More than 700 people have died in nearly 80 drone strikes since August 2008.
Pakistan has publicly criticised drone attacks, saying they fuel support for militants, but observers say the authorities privately condone the strikes.
The American military does not routinely confirm drone operations, but analysts say the US is the only force capable of deploying such aircraft in the region.