A member of al Qaeda's Nusra Front carries his weapon as he squats in the town of the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. A coalition of rebel groups called Jaish al Fateh, or Conquest Army, said it had taken over the city. Syria's al Qaeda offshoot Nusra Front is a major part of the coalition. REUTERS/Ammar Abdullah TPX IMAGES OF THE DAY

A member of al Qaeda's Nusra Front takes down a picture of Syria's President Bashar al-Assad in the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. A coalition of rebel groups called Jaish al Fateh, or Conquest Army, said it had taken over the city. Syria's al Qaeda offshoot Nusra Front is a major part of the coalition. REUTERS/Ammar Abdullah TPX IMAGES OF THE DAY

A member of al Qaeda's Nusra Front climbs on a pole to hang the Nusra flag as others celebrate around a central square in the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. A Syrian insurgent alliance which has captured the last government-held town in the northwestern Idlib province made further advances on Friday, a monitoring group and fighters said. REUTERS/Khalil Ashawi TPX IMAGES OF THE DAY

Members of al Qaeda's Nusra Front fire their weapon during an offensive to take control of the northwestern city of Ariha from forces loyal to Syria's President Bashar al-Assad, in Idlib province May 28, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. REUTERS/Ammar Abdullah 

Men push a bus carrying civilians fleeing the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. A Syrian insurgent alliance which has captured the last government-held town in the northwestern Idlib province made further advances on Friday, a monitoring group and fighters said. REUTERS/Khalil Ashawi TPX IMAGES OF THE DAY

Members of al Qaeda's Nusra Front carry their weapons as they move towards their positions during an offensive to take control of the northwestern city of Ariha from forces loyal to Syria's President Bashar al-Assad, in Idlib province May 28, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. REUTERS/Ammar Abdullah TPX IMAGES OF THE DAY

Residents flee the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. A coalition of rebel groups called Jaish al Fateh, or Conquest Army, said it had taken over the city. Syria's al Qaeda offshoot Nusra Front is a major part of the coalition. REUTERS/Ammar Abdullah TPX IMAGES OF THE DAY

A member of al Qaeda's Nusra Front climbs a pole where a Nusra flag was raised at a central square in the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. A Syrian insurgent alliance which has captured the last government-held town in the northwestern Idlib province made further advances on Friday, a monitoring group and fighters said. REUTERS/Khalil Ashawi

A general view shows the town of the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. A coalition of rebel groups called Jaish al Fateh, or Conquest Army, said it had taken over the city. Syria's al Qaeda offshoot Nusra Front is a major part of the coalition. REUTERS/Ammar Abdullah 

A member of al Qaeda's Nusra Front inspects a burning anti-aircraft vehicle in the town of the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. A coalition of rebel groups called Jaish al Fateh, or Conquest Army, said it had taken over the city. Syria's al Qaeda offshoot Nusra Front is a major part of the coalition. REUTERS/Ammar Abdullah 

Members of the "Army of Fatah" detain a man suspected of being a member of forces loyal to Syria's President Bashar al-Assad in the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. A Syrian insurgent alliance which has captured the last government-held town in the northwestern Idlib province made further advances on Friday, a monitoring group and fighters said. REUTERS/Khalil Ashawi 

Members of al Qaeda's Nusra Front ride on a pick-up truck mounted with an anti-aircraft weapon in the town of the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province, May 29, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. A coalition of rebel groups called Jaish al Fateh, or Conquest Army, said it had taken over the city. Syria's al Qaeda offshoot Nusra Front is a major part of the coalition. REUTERS/Ammar Abdullah 

A member of al Qaeda's Nusra Front burn a Syrian national flag in the town of the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. A coalition of rebel groups called Jaish al Fateh, or Conquest Army, said it had taken over the city. Syria's al Qaeda offshoot Nusra Front is a major part of the coalition. REUTERS/Ammar Abdullah 

Residents flee the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. A coalition of rebel groups called Jaish al Fateh, or Conquest Army, said it had taken over the city. Syria's al Qaeda offshoot Nusra Front is a major part of the coalition. REUTERS/Ammar Abdullah 

Members of al Qaeda's Nusra Front ride on a pick-up truck as they head towards their positions during an offensive to take control of the northwestern city of Ariha from forces loyal to Syria's President Bashar al-Assad, in Idlib province May 28, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. REUTERS/Ammar Abdullah 

Residents carry their belongings as they wait to flee the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. A coalition of rebel groups called Jaish al Fateh, or Conquest Army, said it had taken over the city. Syria's al Qaeda offshoot Nusra Front is a major part of the coalition. REUTERS/Ammar Abdullah 

Members of al Qaeda's Nusra Front ride on a tank as they head towards their positions during an offensive to take control of the northwestern city of Ariha from forces loyal to Syria's President Bashar al-Assad, in Idlib province May 28, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. REUTERS/Ammar Abdullah 

Members of al Qaeda's Nusra Front gather before moving towards their positions during an offensive to take control of the northwestern city of Ariha from forces loyal to Syria's President Bashar al-Assad, in Idlib province May 28, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. REUTERS/Ammar Abdullah 

Rebel fighters of 'Liwa al-Haqq' gather outside a local government complex as one of them walks on a poster of Syria's President Bashar al-Assad in the northwestern city of Ariha, after a coalition of insurgent groups seized the area in Idlib province May 29, 2015. A Syrian insurgent alliance which has captured the last government-held town in the northwestern Idlib province made further advances on Friday, a monitoring group and fighters said. REUTERS/Khalil Ashawi 

A member of al Qaeda's Nusra Front stands behind a vehicle before heading towards his position during an offensive to take control of the northwestern city of Ariha from forces loyal to Syria's President Bashar al-Assad, in Idlib province May 28, 2015. The Syrian army has pulled back from the northwestern city of Ariha after a coalition of insurgent groups seized the last city in Idlib province in northwestern Syria near the Turkish border that was still held by the government. REUTERS/Ammar Abdullah 

Rebel fighters from the Ahrar al-Sham Islamic Movement walk on a hill in Jabal al-Arbaeen, which overlooks the northern town of Ariha, one of the last government strongholds in the Idlib province May 26, 2015. REUTERS/Khalil Ashawi 

A rebel fighter of the Al-Furqan brigade covers his ears as a fellow fighter fires a vehicle's weapon during what the rebels said is an offensive to take control of the al-Mastouma army base which is controlled by forces loyal to Syria's President Bashar al-Assad near Idlib city May 17, 2015. Picture taken May 17, 2015. REUTERS/Khalil Ashawi TPX IMAGES OF THE DAY

Smoke rises from buildings near the national hospital, after what activists said was shelling by warplanes loyal to Syria's President Bashar al-Assad in the town of Jisr al-Shughour, Idlib province May 22, 2015. Syrian soldiers holed up at the hospital besieged by insurgents in northwestern Syria were freed in a military operation on Friday, state TV reported. REUTERS/Ammar Abdullah 

A man gestures as smoke rises from a burning farmland targeted by what activists said were airstrikes by forces loyal to Syria's President Bashar al-Assad in Maarshmarin village in Idlib countryside May 24, 2015. Farmers said that forces loyal to Syria's President Bashar al-Assad are targeting their agriculture lands to destroy their crop. Picture taken May 24, 2015. REUTERS/Khalil Ashawi 

Rebel fighters from the Ahrar al-Sham Islamic Movement take positions inside a building in Jabal al-Arbaeen, which overlooks the northern town of Ariha, one of the last government strongholds in the Idlib province May 26, 2015. REUTERS/Khalil Ashawi 

An Ansar al-Sham brigade fighter carries a head-band which belongs to forces loyal to Syria's President Bashar al-Assad he found after taking control of an area, during an operation to take over Ariha city on one of the frontlines in Idlib governate May 23, 2015. Ariha is one of the last cities in Idlib governorate controlled by forces loyal to Syria's President Bashar Al-Assad, according to the fighters. The writting on the headband reads in Arabic:" Oh Zahraa." (Fatima Al-Zahraa is the daughter of Prophet Muhammad and wife of Imam Ali) REUTERS/Khalil Ashawi 

Rebel fighters gesture after they said they took control of Tel Mastouma, which overlooks the Mastouma military base, south of the city of Idlib, Syria May 18, 2015. Heavy clashes between Syria's army and insurgents erupted around a military base south of Idlib city on Monday as part of a wider battle for control of the northwestern province, Syrian state television and a group monitoring the war said. REUTERS/Ammar Abdullah 

Rebel fighters from the Ahrar al-Sham Islamic Movement run, fearing snipers loyal to Syria's president Bashar Al-Assad, in Jabal al-Arbaeen which overlooks the northern town of Ariha, one of the last government strongholds in the Idlib province May 26, 2015. REUTERS/Khalil Ashawi 

ATTENTION EDITORS - VISUAL COVERAGE OF SCENES OF INJURY

A boy, injured from what activists said was shelling by forces loyal to Syria's President Bashar al-Assad in Ain Larouz village in the Jabal al-Zawiya region, reacts at a field hospital in Idlib province, May 15, 2015. REUTERS/Abed Kontar TPX IMAGES OF THE DAY

A damaged ambulance is seen in the Mastouma military base after rebel fighters seized it, in Idlib May 20, 2015. Insurgents have seized a Syrian army base in Idlib province, a monitoring group said on Tuesday, expanding their grip in the northwestern part of the country. The Syrian Observatory for Human Rights said Syrian troops withdrew from the Mastouma military base after heavy clashes with Islamist-led insurgents and headed towards the northern town of Ariha, one of the last government strongholds in the province. REUTERS/Ammar Abdullah 

A rebel fighter from 'Jaysh al-Sunna' with blood on his forehead sits in a trench during what they said was an offensive to take control of al-Mastouma military camp which is controlled by forces loyal to Syria's President Bashar al-Assad beside Idlib city May 12, 2015. Picture taken May 12, 2015. REUTERS/Khalil Ashawi 

Nusra Front fighters walk among debris caused by what activists said was shelling from warplanes loyal to Syria's President Bashar al-Assad near the national hospital in Jisr al-Shughour town, Idlib province, May 22, 2015. Insurgents on Friday seized the hospital from Syrian government forces who had been besieged there since late April, the Syrian Observatory for Human Rights said, another gain by rebels who have dealt a series of blows to Assad. REUTERS/Ammar Abdullah TPX IMAGES OF THE DAY

A rebel fighter rests along a trench at the frontline where the rebel fighters announced the start of an offensive to take control of Ariha town from forces loyal to Syria's President Bashar al-Assad, in Idlib province May 12, 2015. REUTERS/Ammar Abdullah TPX IMAGES OF THE DAY

Civilians search for belongings amidst rubble after what activists said was an airstrike by forces loyal to Syria's President Bashar al-Assad at a school housing displaced people in al-Muzara village, in the Jabal al-Zawiya region of Idlib province May 11, 2015. REUTERS/Abed Kontar 

Free Syrian Army fighters look up at warplanes loyal to Syria's President Bashar Al-Assad at Nahlaya Front in Idlib, as they gather in preparation for an operation to take over Ariha city, May 9, 2015. Ariha is one of the last cities in Idlib governorate controlled by forces loyal to Assad, according to the fighters. REUTERS/Khalil Ashawi 

Residents inspect a damaged site after what activists said was a barrel bomb dropped by forces loyal to Syria's president Bashar Al-Assad in Maarat Al-Nouman, south of Idlib, May 8, 2015. REUTERS/Khalil Ashawi TPX IMAGES OF THE DAY

A Civil Defence member carries a damaged canister in Ibleen village from what activists said was a chlorine gas attack, on Kansafra, Ibleen and Josef villages, Idlib countryside May 3, 2015. REUTERS/Abed Kontar 

Civil Defence members wear gas masks near damaged ground in Ibleen village from what activists said was a chlorine gas attack, on Kansafra, Ibleen and Josef villages, Idlib countryside May 3, 2015. REUTERS/Abed Kontar 

Debris and smoke rise during what rebel fighters said was an operation in which they blew up a tunnel targeting a post controlled by forces loyal to Syria's President Bashar al-Assad, in Ariha town in Idlib province May 12, 2015. Rebel fighters announced on Tuesday the start of an offensive to take control of Ariha town from government forces. REUTERS/Ammar Abdullah 

A damaged military truck that belonged to forces loyal to Syria's President Bashar al-Assad is seen in Qarmeed camp after Islamist rebel fighters took control of the area, April 26, 2015. A coalition of Islamist rebels seized the army base in northwestern Syria at dawn on Monday after a suicide bomber from al Qaeda's Nusra Front drove a truck packed with explosives into the compound and blew it up. The capture, reported by a rebel commander and social media videos showing militants inside the base, brought the coalition closer to seizing most of Idlib province and moving toward Latakia, the ancestral home of Assad. Picture taken April 26, 2015. REUTERS/Abdalghne Karoof

A rebel fighter rides a motorbike along a road in Qarmeed camp, as smoke rises in the background after Islamist rebel fighters took control of the area from forces of Syria's President Bashar al-Assad, April 27, 2015. A coalition of Islamist rebels seized the army base in northwestern Syria at dawn on Monday after a suicide bomber from al Qaeda's Nusra Front drove a truck packed with explosives into the compound and blew it up. The capture, reported by a rebel commander and social media videos showing militants inside the base, brought the coalition closer to seizing most of Idlib province and moving toward Latakia, the ancestral home of Assad. REUTERS/Abdalghne Karoof TPX IMAGES OF THE DAY