NEW : The number of casualties is unclear . UP : The attackers targeted a lecture hall used by Christians for worship . UP : The attackers opened fire and threw four or five bombs , a journalist says . The attack happened while the university is on a break , so most of the students are not on campus , Tanko said . A university professor says he heard gunfire and multiple explosions .
NEW : The number of casualties is unclear . UP : The attackers targeted a lecture hall used by Christians for worship . UP : The attackers opened fire and threw four or five bombs , a journalist says . A university professor says he heard gunfire and multiple explosions .