A Syrian opposition fighter rubs dust from his face in the Jabilleh neighborhood of the eastern city of Deir al-Zor, during clashes with regime forces as they try to retake the area on February 16, 2013. #

A resident inspects the damages at an ancient Souk caused by what activists said was shelling by forces loyal to Syria's President Bashar al-Assad in Deir al-Zor, on March 9, 2013. #

People walk on a street lined with buildings damaged by what activists said were missiles fired by a Syrian Air Force fighter jet loyal to President Bashar al-Assad in Deir Al-Zor, on March 12, 2013. #

A Syrian street vendor who sells cigarette boxes, sits in front of destroyed shops which were damaged by the shelling of the Syrian forces, at Maarat al-Nuaman town, in Idlib province, on February 26, 2013. Syrian rebels battled government troops near a landmark 12th century mosque in the northern city of Aleppo on Tuesday, while fierce clashes raged around a police academy west of the city, activists said. #

Vehicles burn near a crater on a road after an explosion in central Damascus, on February 21, 2013. Syrian state media blamed what it said was a suicide bombing on "terrorists" battling President Bashar al-Assad. #

In this photo released by the Syrian official news agency SANA, injured Syrians sit on the ground while flames and smoke rise from burned cars after a huge explosion that shook Damascus, on February 21, 2013. #

(1 of 3) Nihal, 9, in the entrance of an underground Roman tomb used as shelter from Syrian government forces shelling and airstrikes, at Jabal al-Zaweya, in Idlib province,on February 28, 2013. Across northern Syria, rebels, soldiers, and civilians are making use of the country's wealth of ancient and medieval antiquities to protect themselves from Syria's two-year-old war. #

(2 of 3) Sami (center) speaks with his children in an underground Roman tomb which he uses with his family as shelter from Syrian government forces, at Jabal al-Zaweya, in Idlib province, on February 28, 2013. The ancient sites are built of thick stone that has already withstood centuries, and are often located in strategic locations overlooking towns and roads. #

(3 of 3) Sobhi al-Hamod, 60, lives with his family in an underground cave used for shelter from Syrian government forces in Idlib province, on February 28, 2013. #

A painting of Syria's President Bashar al-Assad riddled with bullet holes, on the facade of the police academy in Aleppo, after it was captured by Free Syrian Army fighters, on March 4, 2013. #

Firefighters attempt to extinguish a fire at a factory after what activists say was shelling by forces loyal to Syria's President Bashar al-Assad at al-Haidariah area in Aleppo, on February 8, 2013. #

An excavator is used to search for casualties under the rubble at a site hit by what activists said was a Scud missile in Aleppo's Ard al-Hamra neighborhood, on February 23, 2013. Rockets struck eastern districts of Aleppo, Syria's biggest city, killing at least 29 people and trapping a family of 10 in the ruins of their home, activists in the city said. #

A Syrian woman sits on the ruins of her house, which was destroyed in an airstrike by government warplanes a few days earlier, killing 11 members of her family, in the neighborhood of Ansari, Aleppo, on February 6, 2013. #

In this Tuesday March 19, 2013, citizen journalism image provided by Aleppo Media Center AMC which has been authenticated based on its contents and other AP reporting, black smoke rises from buildings due to government forces shelling, in Aleppo. #