Around a quarter of a million civilians are living under siege in rebel-held areas since government forces cut them off last month.
Intense fighting has continued around the Syrian city of Aleppo, where a rebel offensive is trying to break a government siege of rebel-held areas.
The army has been fighting back with the help of Russian air strikes to stop the rebels breaking through.
Over the weekend, the rebels tried to reconnect an encircled area in the east with insurgent territory in the west.
Rebels set off a huge tunnel bomb underneath army positions in the strategic Ramouseh district.
