On Tuesday, several bombs went off inside a Damascus school that activists said was being used by regime forces as a security headquarters. Several people were wounded.
Syria's conflict was the focus of attention as world leaders gathered at the UN General Assembly's annual meeting in New York this week.
UN secretary-general Ban Ki-moon demanded international action to stop the war in Syria, telling a somber gathering of world leaders Tuesday that the 18-month conflict had become "a regional calamity with global ramifications".
Ban, declaring that the situation in Syria is getting worse every day, called the conflict a serious and growing threat to international peace and security that requires attention from the deeply divided UN Security Council.
That appears highly unlikely, however, at least in the near future.
Russia and China have vetoed three Western-backed resolutions aimed at pressuring Assad to end the violence and enter negotiations on a political transition, leaving the UN's most powerful body paralysed in what some diplomats say is the worst crisis since the US-Soviet standoff during the Cold War.
In sharp contrast to the UN chief, President Barack Obama pledged US support for Syrians trying to oust Assad - "a dictator who massacres his own people".