DUBAI (Reuters) -A cleric at a Shi’ite Muslim mosque in the restive, mostly Sunni Muslim Iranian city of Zahedan has been shot dead, the official news agency IRNA said, threatening a spike in sectarian tensions complicating government efforts to contain widespread unrest. IRNA named the dead cleric as Sajjad Shahraki. “A special task force has been formed for the purpose of identifying and arresting the perpetrators,” said Ahmad Taheri, police commander of Sistan-Baluchistan province. Zahedan was the scene of one of the deadliest days during a wave of popular protests that have swept the Islam…