At least 15 Taliban militants, among them a key commander, were killed in on Sunday during security operations in Afghanistan's Farah province."Units of Afghan army launched cleanup operations against Taliban militants in Balablock district and have killed 15 rebels, including their key commander Mawlawi Ibrahim Shiwani who also served as shadow deputy governor for Farah province," a senior security official told Xinhua news agency.The killing of Mawlawi Shiwani could be a major setback to the Taliban militants in Farah and adjoining provinces, he added.