Islamabad , Pakistan ( CNN ) -- Three suspected drone strikes Monday killed 21 people in a volatile northwest Pakistani tribal region that borders Afghanistan , two Pakistani intelligence officials told CNN . The officials , who spoke on condition of anonymity because they were not authorized to speak to the media , said all 21 were militants . However , witnesses told CNN affiliate GEO-TV at the scene that among the dead were seven civilians . CNN can not independently confirm either account . A suspected drone fired at two alleged militant hideoutsin South Waziristan , one of the seven districts of Pakistan 's volatile tribal region bordering Afghanistan . It was the second such series of strikes since Friday in the same area , officials said . Four missiles struck two hideouts in the village of Wacha Dana , killing nine insurgents in one attack and eight in another , said the officials , . A fifth missile struck a vehicle being driven by a suspected militant near the village of Shawal , the officials said . The United States does not comment on suspected drone strikes . But it is the only country in the region known to have the ability to launch missiles from drones -- which are controlled remotely . Based on a count by CNN 's Islamabad bureau , Monday 's suspected drone strike was the 31st this year , compared to 111 in all of 2010 . The U.S. contends insurgents routinely launch attacks from the Pakistani tribal region into Afghanistan , crossing the border to resupply militants with money and weapons .
NEW : The suspected drone strike hits a vehicle and two people in Pakistan 's South Punjab . The U.S. does not comment on suspected drone strikes . Monday 's attack brings to question the number of drone strikes reported this year . The US believes terrorists are crossing into Afghanistan from the region .