Smoke rises from buildings damaged by missiles fired by a Syrian Air Force fighter jet loyal to President Bashar al-Assad in Raqqa province, eastern Syria, March 15, 2013.

Demonstrators shout during a protest in Raqqa, Syria, marking two years since the start of the uprising in the country, March 15, 2013.

Demonstrators shout slogans during a protest against the government of Bashar al-Assad in Istanbul March 15, 2013.

Residents walk past rubbish piled up along a street in Deir al-Zor, Syria, March 13, 2013.

A member of the Free Syrian Army stands near a damaged building in Raqqa province, eastern Syria, March 13, 2013.

Free Syrian Army fighters prepare mortar shells prior to an offensive against forces loyal to Syria's President Bashar al-Assad, in Houla near Homs, March 13, 2013. (Shaam News Network)

Russian Foreign Minister Sergei Lavrov (center) meets with Haitham Manna, the president of the National Coordination Body for Democratic Change in Syria, front left, and secretary Raja al-Nasser, front right, in Moscow, March 11, 2013.

Syrians stand next to dead bodies that have been pulled from the river near Aleppo, March 10, 2012.

Buildings damaged by shelling in the Al-Khalidiya neighborhood of Homs, March 10, 2013.

United Nations High Commissioner for Refugees (UNHCR) Antonio Guterres (C) walks with a Syrian refugee boy at a camp in Nizip, Turkey, March 10, 2013.

Residents walk along a street in Deir al-Zor, March 9, 2013.