 The next day, coordinated attacks claimed by a radical Islamist sect killed at least 143 people in north Nigeria's largest northern city, Kano, a hospital official said Saturday, as gunfire still echoed around some areas of the sprawling city.Since 2009 when the Boko Haram turned violent, Human Rights Watch says the group has been accountable for as many as 935 deaths.In 2011, it was responsible for 510 deaths.