Fighters of the Syria Democratic Forces prepare to fire a mortar shell towards positions held by Islamic State fighters in northern province of Raqqa, Syria May 27, 2016. REUTERS/Rodi Said

Fighters of the Syria Democratic Forces prepare to fire a mortar shell towards positions held by Islamic State fighters in northern province of Raqqa, Syria May 27, 2016. REUTERS/Rodi Said

Fighters of the Syria Democratic Forces prepare to fire a mortar shell towards positions held by Islamic State fighters in northern province of Raqqa, Syria May 27, 2016. REUTERS/Rodi Said

June 14, 2016 11:08 AM (UTC+8)