(CNN) -- A suspected U.S. drone strike in northwestern Pakistan on Monday morning killed 15 militants and wounded three others, a local government official said, the third such deadly attack in as many days.
The drone fired at least six missiles at a militant compound near the town of Mir Ali in the North Waziristan region near the Afghanistan border, government official Muhammad Amir told CNN.
North Waziristan is one of seven districts in Pakistan's tribal region. The area is widely believed to be the operating base for the Haqqani network and other militant groups that have attacked international troops in neighboring Afghanistan.
Monday's attack is the 21st suspected drone strike in Pakistan this year. U.S. officials rarely discuss the CIA's drone program in Pakistan, though privately they have said the covert strikes are legal and an effective tactic in the fight against extremists.
A day earlier, a drone is thought to have fired four missiles that killed nine militants at a militant compound in Wacha Dana, a village in South Waziristan, local government official Javed Marwat told CNN.
This followed a suspected strike Saturday near the town of Wana in the same province that killed two militants riding on a motorcycle, according to Marwat.
U.S. President Barack Obama's administration justified its use of unmanned drones to target suspected terrorists overseas in a rare public statement recently, with John Brennan, the president's top counter-terrorism adviser, saying the strikes are conducted "in full accordance with the law."
The program utilizes unmanned aerial vehicles, often equipped with Hellfire missiles, to target suspected terrorist operatives in remote locations overseas -- with many such strikes occurring in Yemen and Pakistan, despite some internal opposition within that latter South Asian country.
Brennan said the United States "respects national sovereignty and international law" and is guided by the laws of war in ordering those attacks.
CNN's Reza Sayah and journalist Aamir Iqbal contributed to this report.