Rebel fighters walk by damaged buildings near Castello road in Aleppo, Syria September 16, 2016. REUTERS/Abdalrhman Ismail

A general view shows Castello road in Aleppo, Syria September 16, 2016. REUTERS/Abdalrhman Ismail

A rebel fighter walks by damaged buildings near Castello road in Aleppo, Syria September 16, 2016. REUTERS/Abdalrhman Ismail

A general view shows Castello road in Aleppo, Syria September 16, 2016. REUTERS/Abdalrhman Ismail

Civil defense members hold a demonstration to children during a war safety awareness class in Deraa Governorate, Syria. REUTERS/Alaa Al-Faqir

Civil defense members rest amid rubble of damaged buildings after an airstrike on the rebel-held Tariq al-Bab neighborhood of Aleppo, Syria. REUTERS/Abdalrhman Ismail

A Civil Defence member reacts in a damaged site near the frame of a burnt vehicle after an airstrike on al-Jalaa street in the rebel held city of Idlib, Syria. REUTERS/Ammar Abdullah

Smoke rises over a damaged site as Civil Defence members try to put out a fire after an airstrike on al-Jalaa street in the rebel held city of Idlib, Syria. REUTERS/Ammar Abdullah