Ayman al-Zawahiri , al Qaeda deputy leader , was killed by a drone strike , the United States says . His death was a `` very serious blow '' to al Qaeda , al Qaeda says . White House strikes remain highly controversial because of civilian deaths .
Abu Yahya al-Libi , al Qaeda 's deputy leader , was killed by a drone strike , U.S. says . His death was a `` very serious blow '' to al Qaeda , White House says . Drone strikes remain highly controversial because of civilian deaths .