Gas cylinders are displayed for sale on a street in Aleppo, March 24, 2013.

A man sells clothes in Aleppo March 24, 2013.

Free Syrian Army fighters carry weapons while walking down a debris-filled street in Aleppo March 19, 2013.

This citizen journalism image provided by the Aleppo Media Center shows Syrians searching for dead bodies in the rubble of buildings hit by Syrian airstrikes, Aleppo, March 20, 2013.

Syrian President Bashar al-Assad and his wife Asma visit families of students killed during clashes between forces loyal to him and their opponents in Damascus in this handout photograph released by Syria's national news agency SANA on March 20, 2013.

Residents and medics transport a Syrian Army soldier, wounded in what they said was a chemical weapon attack near Aleppo, to a hospital, March 19, 2013.

People wounded in what the Syrian government said was a chemical weapons attack breathe through oxygen masks as they are treated at a hospital in Aleppo, March 19, 2013.

Girls paint their faces with colors of the Syrian revolutionary flag during a fesitval, in Aleppo, Syria, March 20, 2013.

A citizen journalism image of black smoke rising from a building hit by Syrian government shelling, Aleppo, March 19, 2013.