By Saud Mehsud
DERA ISMAIL KHAN, Pakistan (Reuters) - U.S. drone aircraft struck twice in Pakistan's unruly tribal regions along the border with Afghanistan on Tuesday, killing 15 suspected militants, including two senior militant commanders, security and intelligence officials said.
In the first strike, a drone fired missiles at a vehicle in the Birmal area of the South Waziristan tribal region, killing eight.
Among the dead were Shams Ullah and Amir Hamza, senior commanders of a pro-government militant faction led by Maulvi Nazir, one of the most influential militant leaders in the region.
Seven suspected militants were killed in the second attack later in the day, when a drone fired missiles at a vehicle in the Sara Khawra area, which straddles the border between North Waziristan and South Waziristan.
Several militant groups, including the Afghan Taliban and al Qaeda, operate in Pakistan's semi-autonomous border regions, taking advantage of a porous border with Afghanistan to conduct cross-border attacks or plot violence elsewhere.
The usually unacknowledged Central Intelligence Agency's drone program, an important element of the U.S. counter-terrorism strategy in the region, appeared to have been halted after a NATO cross-border air attack killed 24 Pakistani soldiers last November, sparking fury in Pakistan.
The campaign, using remotely-piloted armed aircraft, resumed on January 10.
The use of drones is opposed by most Pakistani politicians and the public, who consider drone strikes violations of sovereignty with unacceptable civilian casualties.
Despite public opposition, Pakistan has quietly supported the program, which U.S. President Barack Obama ramped up after taking office in 2009.
(Additional reporting by Hafiz Wazir in WANA, Jibran Ahmad in PESHAWAR, Mustansar Baloch in DERA ISMAIL KHAN, Haji Mujtaba in MIRANSHAH, and Ali Afzaal in PARACHINAR; Writing by Mahawish Rezvi; Editing by Chris Allbritton and Daniel Magnowski)
(This story was corrected to fix Nazir's affiliation)