Rebel fighters work on the tracks of armoured vehicles after seizing them from forces loyal to Syria's President Assad, at Abu Alaa checkpoint in Khan Sheikhoun
Rebel fighters work on the tracks of armoured vehicles after seizing them from forces loyal to Syria's President Bashar al-Assad, at Abu Alaa checkpoint in Khan Sheikhoun, northern Idlib province May 28, 2014. A workshop was established to teach rebel fighters how to repair and drive military vehicles, according to the rebel fighters. Picture taken May 28, 2014. REUTERS/ Khalil Ashawi (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT)
A rebel fighter gestures as others drive armoured vehicles seized from forces loyal to Syria's President Assad at Abu Alaa checkpoint in Khan Sheikhoun
A rebel fighter gestures as others drive armoured vehicles seized from forces loyal to Syria's President Bashar al-Assad at Abu Alaa checkpoint in Khan Sheikhoun, northern Idlib province May 28, 2014. A workshop was established to teach rebel fighters how to repair and drive military vehicles, according to the rebel fighters. Picture taken May 28, 2014. REUTERS/ Khalil Ashawi (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT)
Rebel fighters install the tracks for a BMP armoured vehicle, after seizing it from forces loyal to Syria's President Assad at Abu Alaa checkpoint in Khan Sheikhoun
Rebel fighters install the tracks for a BMP armoured vehicle, after seizing it from forces loyal to Syria's President Bashar al-Assad at Abu Alaa checkpoint in Khan Sheikhoun, northern Idlib province May 28, 2014. A workshop was established to teach rebel fighters how to repair and drive military vehicles, according to the rebel fighters. Picture taken May 28, 2014. REUTERS/ Khalil Ashawi (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT)
Rebel fighters install the tracks for a BMP armoured vehicle, after seizing it from forces loyal to Syria's President Assad at Abu Alaa checkpoint in Khan Sheikhoun
Rebel fighters install the tracks for a BMP armoured vehicle, after seizing it from forces loyal to Syria's President Bashar al-Assad at Abu Alaa checkpoint in Khan Sheikhoun, northern Idlib province May 28, 2014. A workshop was established to teach rebel fighters how to repair and drive military vehicles, according to the rebel fighters. Picture taken May 28, 2014. REUTERS/ Khalil Ashawi (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT)
Men gather at a site hit by what activists said was a barrel bomb in al-Qarlaq neighbourhood of Aleppo
Men gather at a site hit by what activists said was a barrel bomb dropped by forces loyal to Syria's President Bashar al-Assad in al-Qarlaq neighbourhood of Aleppo May 29, 2014. REUTERS/Jalal Al-Mamo (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT)
Civilians help an injured man at a site hit by what activists said was a barrel bomb in al-Qarlaq neighbourhood of Aleppo
Civilians help an injured man at a site hit by what activists said was a barrel bomb dropped by forces loyal to Syria's President Bashar al-Assad in al-Qarlaq neighbourhood of Aleppo May 29, 2014. REUTERS/Jalal Al-Mamo (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT)
Civil Defence members, rebel fighters and civilians search for survivors at a site hit by what activists said was a barrel bomb in al-Qarlaq neighbourhood of Aleppo
Civil Defence members, rebel fighters and civilians search for survivors at a site hit by what activists said was a barrel bomb dropped by forces loyal to Syria's President Bashar al-Assad in al-Qarlaq neighbourhood of Aleppo May 29, 2014. REUTERS/Jalal Al-Mamo (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT)
Civil Defence members, rebel fighters and civilians search for survivors at a site hit by what activists said was a barrel bomb in al-Qarlaq neighbourhood of Aleppo
Civil Defence members, rebel fighters and civilians search for survivors at a site hit by what activists said was a barrel bomb dropped by forces loyal to Syria's President Bashar al-Assad in al-Qarlaq neighbourhood of Aleppo May 29, 2014. REUTERS/Jalal Al-Mamo (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT TPX IMAGES OF THE DAY)
Civil Defence members, rebel fighters and civilians search for survivors at a site hit by what activists said was a barrel bomb in al-Qarlaq neighbourhood of Aleppo
Civil Defence members, rebel fighters and civilians search for survivors at a site hit by what activists said was a barrel bomb dropped by forces loyal to Syria's President Bashar al-Assad in al-Qarlaq neighbourhood of Aleppo May 29, 2014. REUTERS/Jalal Al-Mamo (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT)
Civil Defence members, rebel fighters and civilians search for survivors at a site hit by what activists said was a barrel bomb in al-Qarlaq neighbourhood of Aleppo
Civil Defence members, rebel fighters and civilians search for survivors at a site hit by what activists said was a barrel bomb dropped by forces loyal to Syria's President Bashar al-Assad in al-Qarlaq neighbourhood of Aleppo May 29, 2014. REUTERS/Jalal Al-Mamo (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT)