You can see Al Nusra Front’s flag on one of their vehicles.

Via IPT:

While the civil war in Syria is between Bashar al-Assad’s Alwaite regime and the overwhelmingly Sunni rebels, the neutral Christian and Druze minorities in Damascus are paying a high price. Regime forces are using Christians and Druze neighborhoods as a base to launch their attacks against rebel-controlled areas, and in return, the rebels are retaliating by launching mortars against neighborhoods packed with civilian residents. […]

The mortar campaign has been active since a month. A group called Faylak Al Ruhman has claimed responsibility for the shelling. It claims to be targeting Assad forces and the Shia Iraqi militia that is allied with Assad, both of which are using the Christian and Druze neighborhood as a base. The Youtube channel of Faylak Al Rahman has posted a video showing rebels while firing the mortars against the city of Jaramana.

It is difficult to believe that these mortars are being fired at military targets. They are not guided missiles, but very crude rockets. Christians and Druze in Syria are not only blaming the rebels, but the regime, too, for putting them on the front line of its battle against the rebel forces.