At least three militants were killed on Friday in the second US missile strike in as many days targeting Pakistan's wild tribal region of North Waziristan, officials said.
The morning attack by a drone aircraft struck a suspected militant hideout in Ghundikala village, 15 kilometres (nine miles) east of Miranshah, the main town of North Waziristan and close to the Afghan border.
"A US drone fired two missiles, targeting a vehicle and killing three militants," a senior security official in the area said.
"The identity of militants is not known yet. It is also not clear whether any high value target was present in the area when the attack took place."
Another security official confirmed the strike and the casualties. Both officials requested anonymity because of the sensitivity of the US strikes in Pakistan, which have inflamed anti-American sentiment.
It was not clear which group was targeted, with North Waziristan rife with Taliban militants, Al-Qaeda fighters and members of the Haqqani network, a powerful group known for staging attacks on foreign troops in Afghanistan.
The bombing comes the morning after a similar US drone attack killed four militants Machikhel village, about 25 kilometres east of Miranshah.
The region has seen a rise in US strikes, which fan anti-Americanism in the nuclear-armed Muslim country, since US President Barack Obama took office and put the country on the frontline of the war on Al-Qaeda.
His administration is pressuring Islamabad to crack down not only the Pakistani Taliban, but also Al-Qaeda fighters and militants who cross the border and attack US and NATO forces stationed in Afghanistan.
North Waziristan neighbours South Waziristan, where Pakistan has been focusing its most ambitious offensive yet against homegrown Taliban militants, sending about 30,000 troops into the region on October 17.