U.S. reasonably certain British IS leader Jihadi John killed in Syria

By Idrees Ali and Mariam Karouny WASHINGTON/BEIRUT (Reuters) - The U.S. military said on Friday it was "reasonably certain" a drone strike had killed Jihadi John, Islamic State's "lead executioner" and a symbol of the militant group's brutality. British Prime Minister David Cameron said he could not yet confirm the death of Mohammed Emwazi, who had become known as Jihadi John after appearing in videos showing the killings of U.S. and British hostages. "If this strike was successful -- and we sti