KABUL, Afghanistan—A bomb ripped through a mosque in northern Kabul during Friday prayers, killing 12 worshippers, and wounding 15, Afghan police said. No one immediately claimed responsibility for the bombing, the latest in a surge in violence as U.S. and NATO troops have begun their final withdrawal from the country, after 20 years of war. According to Afghan police spokesman, Ferdaws Faramarz, the bomb exploded as prayers had begun. The mosque’s imam, Mofti Noman, was among the dead, the spokesman said and added that the initial police investigation suggests the imam may have been the target. Taliban spokesman Zabihullah Mujahid denied any insurgent connection to the mosque attack, condemning it and accusing Afghanistan’s intelligence agency of being behind the explosion. Both the Taliban and government routinely blame each other for attacks. The attackers are rarely identified, and the public is seldom informed of the results of investigations into the many …