Ayman al-Zawahiri , al Qaeda deputy leader , was killed by a drone strike , the United States says . The strike on Monday that killed al-Libi is believed to be the 21st U.S. drone strike in the country this year . His death was a `` very serious blow '' to al Qaeda , al Qaeda says . White House strikes remain highly controversial because of civilian deaths .
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 .