Hundreds of thousands of Shi'ite Muslims are descending on the Iraqi city of Karbala for the Ashoura religious ritual. Security is very tight - Sunni extremists have targeted the event in the past. Ashoura is one of the holiest days for Shi'ites - but tensions are especially high this year, with Islamic State controlling large parts of north and west Iraq. Read more: www.dw.de/english