Nigerian troops have killed Boko Haram spokesman Abu Qaqa, the public messenger of an Islamic sect that has become the biggest threat to Nigeria's security. It happened in a gun battle in the northern city of Kano. Boko Haram has killed hundreds of people since 2009 in attacks on security forces, government offices and churches. The organization has been designated a terrorist group by the United States, which means it's subject to sanctions and possible military strikes.