WASHINGTON -- Contrary to assurances it has deployed U.S. drones only against known senior leaders of al Qaida and allied groups, the Obama administration has targeted and killed hundreds of suspected lower-level Afghan, Pakistani and unidentified “other” militants in scores of strikes in Pakistan’s rugged tribal area, classified U.S. intelligence reports show.

The administration has said that strikes by the CIA’s missile-firing Predator and Reaper drones are authorized only against “specific senior operational leaders of al Qaida and associated forces” involved in the Sept. 11, 2001, terror attacks who are plotting “imminent” violent attacks on Americans.

“It has to be a threat that is serious and not speculative,” President Barack Obama said in a Sept. 6, 2012, interview with CNN. “It has to be a situation in which we can’t capture the individual before they move forward on some sort of operational plot against the United States.”

Copies of the top-secret U.S. intelligence reports reviewed by McClatchy, however, show that drone strikes in Pakistan over a four-year period didn’t adhere to those standards.

The intelligence reports list killings of alleged Afghan insurgents whose organization wasn’t on the U.S. list of terrorist groups at the time of the 9/11 strikes; of suspected members of a Pakistani extremist group that didn’t exist at the time of 9/11; and of unidentified individuals described as “other militants” and “foreign fighters.”

In a response to questions from McClatchy, the White House defended its targeting policies, pointing to previous public statements by senior administration officials that the missile strikes are aimed at al Qaida and associated forces.

Micah Zenko, an expert with the Council on Foreign Relations, a bipartisan foreign policy think tank, who closely follows the target killing program, said McClatchy’s findings indicate that the administration is “misleading the public about the scope of who can legitimately be targeted.”

The documents also show that drone operators weren’t always certain who they were killing despite the administration’s guarantees of the accuracy of the CIA’s targeting intelligence and its assertions that civilian casualties have been “exceedingly rare.”

McClatchy’s review is the first independent evaluation of internal U.S. intelligence accounting of drone attacks since the Bush administration launched America’s secret aerial warfare on Oct. 7, 2001, the day a missile-carrying Predator took off for Afghanistan from an airfield in Pakistan on the first operational flight of an armed U.S. drone.

The analysis takes on additional significance because of the domestic and international debate over the legality of drone strikes in Pakistan amid reports that the administration is planning to broaden its use of targeted killings in Afghanistan and North Africa.

The U.S. intelligence reports reviewed by McClatchy covered most – although not all – of the drone strikes in 2006-2008 and 2010-2011. In that later period, Obama oversaw a surge in drone operations against suspected Islamist sanctuaries on Pakistan’s side of the border that coincided with his buildup of 33,000 additional U.S. troops in southern Afghanistan. Several documents listed casualty estimates as well as the identities of targeted groups.