At least 21 people were killed and 50 hurt on Sunday in a rebel mortar attack on regime-held districts of the Syrian city of Aleppo, a monitoring group said. “The fire targeted regime-held neighbourhoods, including some in the Old City where the rebels are trying to advance,” said the Britain-based Syrian Observatory for Human Rights. Aleppo is divided between Government and Opposition control, and clashes on the ground, rebel fire and regime aerial bombardment have all increased there in recent weeks.