Nasiruddin's presence in the Pakistani capital could raise questions in Washington. U.S. officials have accused Pakistan's intelligence agency of supporting the Haqqani network as a key proxy in the Afghan war—an allegation denied by Islamabad.
No one has yet claimed responsibility for the killing, but it will likely spark suspicion in Pakistan that the Americans were behind it.
Nasiruddin's death comes less than two weeks after the United States outraged Pakistani officials by killing Pakistani Taliban leader Hakimullah Mehsud in a drone strike a day before the government planned to invite him to peace talks.