Kurdish fighters from the People's Protection Units (YPG) fires rifles at a drone operated by Islamic State militants in Raqqa, Syria June 16, 2017. REUTERS/Goran Tomasevic

A member of Roj Mine Control Organization searches for mines and explosive devices planted by Islamic State militants to disarm them near Ain Issa village north of Raqqa, Syria, June 20, 2017. REUTERS/Goran Tomasevic

A woman sits in a van next to a coffin of a Syrian Democratic Forces (SDF) fighter killed by Islamic State militants in Raqqa, during a funeral in Tal Abiad, Syria June 23, 2017. REUTERS/Goran Tomasevic

Kurdish fighters from the People's Protection Units (YPG) stand in a house in Raqqa, Syria June 21, 2017. REUTERS/Goran Tomasevic

A fighter from SDF flies a drone in western Raqqa province, Syria June 18, 2017. REUTERS/Rodi Said

Image for illustrative purpose. A Kurdish fighter from the People's Protection Units (YPG) looks at a smoke after an coalition airstrike in Raqqa, Syria June 16, 2017. REUTERS/Goran Tomasevic

Syrian Democratic Forces (SDF) fighters sit next to a coffin of a Syrian Democratic Forces (SDF) fighter killed by Islamic State militants in Raqqa, during a funeral in Tal Abiad, Syria June 23, 2017. REUTERS/Goran Tomasevic

A Kurdish fighter from the People's Protection Units (YPG) fires a rocket in Raqqa, Syria, June 15, 2017. REUTERS/Goran Tomasevic

A Kurdish fighter from the People's Protection Units (YPG) carries ammunition in Raqqa, Syria June 21, 2017. REUTERS/Goran Tomasevic

A Syrian Democratic Forces (SDF) fighter stands at a cemetery during a funeral for Syrian Democratic Forces (SDF) fighters killed by Islamic State militants in Raqqa, at Tal Abiad, Syria June 23, 2017. REUTERS/Goran Tomasevic

A female Kurdish fighter from the People's Protection Units (YPG) fires a long range sniper rifle at Islamic State militants in Raqqa, Syria June 18, 2017. REUTERS/Goran Tomasevic

Image for illustrative purpose. A Kurdish fighter from the People's Protection Units (YPG) reacts on a sound of a drone operated by Islamic State militants in Raqqa, Syria June 16, 2017. REUTERS/Goran Tomasevic

Syrian Democratic Forces (SDF) fighters stand in line during a funeral of SDF fighters killed by Islamic State militants in Raqqa, at Tal Abiad, Syria June 23, 2017. REUTERS/Goran Tomasevic

A Kurdish fighter from the People's Protection Units (YPG) attaches a detonator to a rocket in Raqqa, Syria, June 15, 2017. REUTERS/Goran Tomasevic

Kurdish fighters from the People's Protection Units (YPG) stand outside a house in Raqqa, Syria June 21, 2017. REUTERS/Goran Tomasevic

Syrian Democratic Forces (SDF) fighters inspect a tunnel dug by Islamic State militants inside a house in the Raqqa's al-Sanaa industrial neighbourhood, Syria June 14, 2017. Picture taken June 14, 2017. REUTERS/Rodi Said

Kurdish fighters from the People's Protection Units (YPG) extinguish a fire in a wheat field burned during clashes with Islamic State militants in Raqqa, Syria, June 15, 2017. REUTERS/Goran Tomasevic

Kurdish fighters from the People's Protection Units (YPG) stand outside a house in Raqqa, Syria June 21, 2017. REUTERS/Goran Tomasevic

A Kurdish fighter from the People's Protection Units (YPG) looks out of a window in Raqqa, Syria June 18, 2017. REUTERS/Goran Tomasevic

A Kurdish fighter from the People's Protection Units (YPG) rests in house in Raqqa, Syria June 16, 2017. REUTERS/Goran Tomasevic

Syrian Democratic Forces (SDF) fighters carry coffins of SDF fighters killed by Islamic State militants in Raqqa, during a funeral in Tal Abiad, Syria June 23, 2017. REUTERS/Goran Tomasevic

A female Kurdish fighter from the People's Protection Units (YPG) rests in Raqqa, Syria, June 15, 2017. REUTERS/Goran Tomasevic

Kurdish fighters from the People's Protection Units (YPG) stand in a house in Raqqa, Syria June 21, 2017. REUTERS/Goran Tomasevic