Internally displaced Syrians who fled Raqqa tie ropes for their tents in a camp in Manbij, Syria on April 6, 2017. (Photo by Rodi Said/Reuters)





A Syrian man and girl flee following a reported government air strike on the rebel- controlled town of Hamouria, in the eastern Ghouta region on the outskirts of the capital Damascus, on April 4, 2017. (Photo by Abdulmonam Eassa/AFP Photo)





Syrians from the government- held towns of Fuaa and Kafraya, which have been under crippling siege for more than two years, reach with buses the edge of the rebel- held transit point of Rashidin outside government- held second city Aleppo, on April 19, 2017. The evacuation of civilians and fighters from besieged Syrian towns resumed after a weekend bombing at a transit point killed 126 people, 68 of them children, an AFP correspondent reported. (Photo by Omar Haj Kadour/AFP Photo)





Members of the Syrian civil defence volunteers, also known as the White Helmets, remove a victim from the rubble of his house on April 8, 2017, following a reported air strike by government forces on a rebel- held area in the southern Syrian city of Daraa. (Photo by Mohamad Abazeed/AFP Photo)





A Syrian mourns as members of the Syrian civil defence volunteers, also known as the White Helmets, and people search for survivors from the rubble following reported air- strikes on the rebel- held town of Saqba, in Eastern Ghouta, on April 4, 2017. (Photo by Amer Almohibany/AFP Photo)





Wrecked vehicles are seen amidst debris following air strikes on the rebel- held village of Kafr Tekharim in northwest Syria early on April 25, 2017 in which 12 people were killed 12 people and put a nearby field clinic out of service. (Photo by Omar Haj Kadour/AFP Photo)





A displaced Syrian girl walks holding a pot at the al-Mabrouka camp in the village of Ras al-Ain on the Syria-Turkey border, where many Syrians who fled from territory held by the Islamic State (IS) group in Deir Ezzor and Raqa are taking shelter on April 23, 2017. (Photo by Delil Souleiman/AFP Photo)





An unconscious Syrian child receives treatment at a hospital in Khan Sheikhun, a rebel-held town in the northwestern Syrian Idlib province, following a suspected toxic gas attack on April 4, 2017. A suspected chemical attack killed at least 58 civilians including several children in rebel-held northwestern Syria, a monitor said, with the opposition accusing the government and demanding a UN investigation. (Photo by Omar Haj Kadour/AFP Photo)





A civil defence member breathes through an oxygen mask, after what rescue workers described as a suspected gas attack in the town of Khan Sheikhoun in rebel-held Idlib, Syria April 4, 2017. (Photo by Ammar Abdullah/Reuters)





Smoke rises while a man herds sheep after an airstrike on rebel-held Daraa Al-Balad, Syria April 7, 2017. (Photo by Alaa Al-Faqir/Reuters)





A Syrian Democratic Forces (SDF) fighter inspects a damaged building inside Tabqa military airport after taking control of it from Islamic State fighters, west of Raqqa city, Syria April 9, 2017. (Photo by Rodi Said/Reuters)





Syrian Democratic Forces (SDF) female fighters carry water supplies on the bank of the Euphrates river, west of Raqqa city, Syria April 10, 2017. (Photo by Rodi Said/Reuters)





A rebel fighter stands on a vehicle near buses carrying people that evacuated from the two villages of Kefraya and al-Foua, after an agreement reached between rebels and Syria's army, at insurgent-held al-Rashideen, Aleppo province, Syria April 14, 2017. (Photo by Ammar Abdullah/Reuters)





People that were evacuated from the two villages of Kefraya and al-Foua walk near buses, after a stall in an agreement between rebels and Syria's army, at insurgent-held al-Rashideen, Aleppo province, Syria April 15, 2017. (Photo by Ammar Abdullah/Reuters)





A damaged bus is seen after an explosion yesterday at insurgent-held al-Rashideen, Aleppo province, Syria April 16, 2017. (Photo by Ammar Abdullah/Reuters)





Scattered shoes lie on the ground near damaged buses after an explosion yesterday at insurgent-held al-Rashideen, Aleppo province, Syria April 16, 2017. (Photo by Ammar Abdullah/Reuters)





A man inspects a line of bread to be distributed as aid in the rebel held besieged city of Douma, in the eastern Damascus suburb of Ghouta, Syria April 15, 2017. Picture taken April 15, 2017. The bakery was reopened by the Unified Aid Office, which is in charge of distributing aid in eastern Ghouta, to alleviate the impact of a rise in bread prices to $2 per kg, according to the men running the bakery. (Photo by Bassam Khabieh/Reuters)





An internally displaced girl, who fled with others the shelling on the southern city of Deraa, looks out from a tent in the surrounding plains of the city, Syria April 20, 2017. (Photo by Alaa Al-Faqir/Reuters)





People who were evacuated from four besieged towns, as part of a reciprocal evacuation deal, travel to their respective destinations with one convoy (R) going to rebel-held Idlib and another convoy (L) to government-held Aleppo, as they wait at a transit point in al-Rashideen, Syria April 21, 2017. (Photo by Ammar Abdullah/Reuters)





Syrian children wait to receive treatment at a makeshift clinic following reported air strikes by government forces in the rebel-held town of Douma, on the eastern outskirts of Damascus, on April 4, 2017. (Photo by Abd Doumany/AFP Photo)





An opposition fighter walks in a field of poppies in a rebel-held area in the southern Syrian city of Daraa on April 10, 2017. (Photo by Mohamad Abazeed/AFP Photo)





Internally Displaced Syrian kids, fled from their homes due to the Assad Regime forces' attacks on civilians and siege for more than 6 years, pose for a photo as they try to live at a makeshift tent camp, in Eastern Ghouta of Damascus, Syria on April 19, 2017. (Photo by Kaled Abu Jaafer/Anadolu Agency/Getty Images)





In this picture taken on Tuesday April 4, 2017, SAbdul-Hamid Alyousef, 29, holds his twin babies who were killed during a suspected chemical weapons attack, in Khan Sheikhoun in the northern province of Idlib, Syria. Alyousef also lost his wife, two brothers, nephews and many other family members in the attack that claimed scores of his relatives. The death toll from a suspected chemical attack on a northern Syrian town rose to 72 on Wednesday as activists and rescue workers found more terrified survivors hiding in shelters near the site of the harrowing assault, one of the deadliest in Syria's civil war. (Photo by Alaa Alyousef via AP Photo)





In this photo released by the Syrian official news agency SANA, Syrian government forces welcome a bus carry Syrian citizens and pro-government fighters who evacuated from the two pro-government villages of Foua and Kfarya, upon their arrival at a cross point between the rebels and the Syrian government forces on the outskirts of Aleppo city, Syria, Friday, April, 21, 2017. Syrian state TV says the troubled population transfers involving thousands of Syrians have resumed after stalling for days following a massive explosion that killed dozens. (Photo by SANA via AP Photo)





In this photo released by the Syrian official news agency SANA, Syrian government forces, left, welcome a bus carry Syrian citizens and pro-government fighters who evacuated from the two pro-government villages of Foua and Kfarya, upon their arrival at a cross point between the rebels and the Syrian government forces on the outskirts of Aleppo city, Syria, Friday, April, 21, 2017. (Photo by SANA via AP Photo)





In this photo released by the Syrian official news agency SANA, buses carry Syrian citizens who evacuated from the two pro-government villages of Foua and Kfarya, pass in front of damaged buildings upon their arrival at a handover point between the two rebels and the Syrian forces on the outskirts of Aleppo city, Syria, Friday, April, 21, 2017. (Photo by SANA via AP Photo)





A man inspects a piece of a rocket that landed south of Daraa Al-Balad, Syria, April 5, 2017. (Photo by Alaa Al-Faqir/Reuters)