A man runs with an injured child at a damaged site after what activists said was shelling by forces loyal to Syria's president Bashar al-Assad on Al-Dubeit neighborhood in Idlib city, after rebels took control of the area April 5, 2015. REUTERS/Ammar Abdallah TPX IMAGES OF THE DAY

A civilian sits at a doorstep at a site hit by what activists said were air strikes by forces loyal to Syria's President Bashar al-Assad, in al-Naaoura district of Idlib, after Islamist rebel fighters took control of the area, April 7, 2015. REUTERS/Ammar Abdullah 

Islamist rebel fighters ride on a motorbike along a deserted street in Idlib city April 6, 2015. Idlib, around 30 km (20 miles) from the Turkish border is only the second provincial capital to slip from government hands after Raqqa in the east, which Islamic State has turned into its de facto capital. REUTERS/Ammar Abdullah 

Residents and rebel fighters inspect fire at a damaged site after what activists said was shelling by forces loyal to Syria's president Bashar al-Assad on Al-Dubeit neighborhood in Idlib city, after rebels took control of the area April 5, 2015. REUTERS/Ammar Abdallah TPX IMAGES OF THE DAY

A rebel fighter, affected by what activists said was a gas attack, receives treatment with the help of members of the Syrian Arab Red Crescent and Civil Defense in Idlib city March 31, 2015. Islamist groups including al Qaeda's Nusra Front have seized the city of Idlib for the first time in Syria's civil war, fighters and a monitoring group said on Saturday. REUTERS/Abed Kontar 

An Islamist rebel fighter drives a motorcycle along a street after receiving humanitarian aid from a relief organization in Idlib city April 1, 2015. Nusra Front on Thursday declared that Idlib, which was seized from government forces on Saturday by a coalition of militant groups, would now be ruled according to sharia law. Picture taken April 1, 2015. REUTERS/Ammar Abdullah 

A defaced picture of Syria's President Bashar al-Assad is pictured on the facade of Idlib museum in Idlib city, after Islamist rebel fighters took control of the area, April 1, 2015. Islamist groups including al Qaeda's Nusra Front have seized the city of Idlib for the first time in Syria's civil war, fighters and a monitoring group said on Saturday. Idlib museum was emptied last year by the Syrian government who transported all the archeological artifacts to safe storages. REUTERS/Mohamad Bayoush 

A woman carrying a child reacts at a damaged site after what activists said was shelling by forces loyal to Syria's president Bashar al-Assad on a mosque in Idlib city, after rebels took control of the area April 3, 2015. REUTERS/Ammar Abdallah 

Members of al Qaeda's Nusra Front man a checkpoint in Idlib March 30, 2015. Islamist groups including al Qaeda's Nusra Front have seized the city of Idlib for the first time in Syria's civil war, fighters and a monitoring group said on Saturday. REUTERS/Abed Kontar 

A man stands near confiscated cigarettes set on fire by members of al Qaeda's Nusra Front in Idlib city March 31, 2015. Islamist groups including al Qaeda's Nusra Front have seized the city of Idlib for the first time in Syria's civil war, fighters and a monitoring group said on Saturday. Picture taken March 31, 2015. REUTERS/Ammar Abdullah 

Rebel fighters from Suqour al-Sham Brigade sit with their weapons inside a trench during clashes with forces loyal to Syria's president Bashar al-Assad as they flee Idlib city, after rebel fighters took control of the area, on Al-Mastumah hill March 28, 2015. REUTERS/Mohamad Bayoush 

Residents flee Idlib city fearing airstrikes from forces loyal to Syria's president Bashar Al-Assad, after rebel fighters took control of the area March 28, 2015. REUTERS/Khalil Ashawi

Rebel fighters from Suqour al-Sham Brigade fire their weapons towards forces loyal to Syria's president Bashar al-Assad that are fleeing Idlib city, after rebel fighters took control of the area, on Al-Mastumah hill March 28, 2015. REUTERS/Mohamad Bayoush 

Men search under the rubble of damaged buildings at a site hit by what activists said were air strikes by forces of Syria's President Bashar al-Assad in Idlib city April 1, 2015. Islamist groups including al Qaeda's Nusra Front have seized the city of Idlib for the first time in Syria's civil war, fighters and a monitoring group said on Saturday. REUTERS/Mohamad Bayoush 

Rebel ride a tank in Idlib city, after they took control of the area March 28, 2015. Picture taken March 28, 2015. REUTERS/Mohamad Bayoush 

An Islamist rebel fighter sits at his guard post in Idlib city April 1, 2015. Nusra Front on Thursday declared that Idlib, which was seized from government forces on Saturday by a coalition of militant groups, would now be ruled according to sharia law. Picture taken April 1, 2015. REUTERS/Ammar Abdullah 

A man carries water bottles in a damaged area from what activists said was due to shelling from forces loyal to Syria's President Bashar al-Assad in Idlib city, after rebels took control of the area March 29, 2015. REUTERS/Mahmoud Hebbo 

Children play in Idlib city April 1, 2015. Nusra Front on Thursday declared that Idlib, which was seized from government forces on Saturday by a coalition of militant groups, would now be ruled according to sharia law. Picture taken April 1, 2015. REUTERS/Ammar Abdullah 

A man stands on top of a damaged sculpture of late Syrian president Hafez al-Assad, father of Syrian President Bashar al-Assad, in Idlib city, after rebel fighters took control of the area March 28, 2015. REUTERS/Khalil Ashawi

A damaged picture of Syrian president Bashar Al-Assad is seen on a wall in Idlib city, after rebel fighters took control of the area March 28, 2015. The text on the poster reads in Arabic "With Bashar". Picture taken March 28, 2015. REUTERS/Ammar Abdallah