PESHAWAR, Pakistan—Officials vowed Saturday to hunt down and arrest the masterminds behind a deadly mosque attack in Pakistan a day earlier claimed by an affiliate of the ISIS terrorist group. The assault killed 63 people and wounded nearly 200. ISIS said in a statement the lone suicide bomber was from neighboring Afghanistan. He shot two police guarding the Shiite Muslim mosque in northwest Peshawar before entering inside and exploding his device, it said. The attack took place as worshipers knelt in Friday prayer. The ISIS affiliate, known as ISIS in Khorasan Province (ISIS-K), is headquartered in eastern Afghanistan. The Taliban in Afghanistan, who have been fighting ISIS, condemned the attack. ISIS has proven to be the Taliban terrorist group’s greatest security threat since sweeping into power last August. The Taliban refused to comment on the ISIS claim that the suicide bomber was Afghan. The death toll was likely to continue …