A picture taken on July 1, 2014 shows a North Oil Company gas field located near a checkpoint held by militants of the Islamic State (IS), some 30 kilometres southwest of the disputed Iraqi city of Kirkuk. Iraqi security forces and loyalists are battling militants led by the Islamic State (IS), which on June 30 declared a 'caliphate,' an Islamic form of government last seen under the Ottoman Empire, and ordered Muslims worldwide to pledge allegiance to their chief. AFP PHOTO / MARWAN IBRAHIM        (Photo credit should read MARWAN IBRAHIM/AFP/Getty Images)