Nigerian opposition presidential candidate urges calm after election postponement

By Julia Payne ABUJA (Reuters) - Nigerian opposition presidential candidate general Muhammadu Buhari called for calm in the country and cautioned against any violence following postponement of elections. Foreign powers are closely observing the course of elections in Africa's biggest economy and have voiced concerns there could be a repetition of violence that followed 2011 elections when 800 people died. "Any act of violence can only complicate the security challenges in the country a