By Stephanie van den Berg THE HAGUE (Reuters) -A suspected leader of the Seleka militia groups in the Central African Republic, Mahamat Said Abdel Kani, pleaded not guilty on Monday to charges of war crimes and crimes against humanity at the opening of his trial at the International Criminal Court. Prosecutors said Said oversaw a prison in the capital Bangui where inmates were beaten and tortured. “I plead not guilty to all charges and all situations,” Said, dressed in a dark grey suit, told the judges. The mostly Muslim Seleka militia groups seized power in 2013-2014 as part of the Central Af…