Rebel mortar fire on government-held districts of the Syrian city ofAleppo killed at least 21 people and wounded 50 on Sunday, a monitoring groupsaid."The fire targeted regime-held neighbourhoods, including some in the Old Citywhere the rebels are trying to advance," the Britain-based Syrian Observatory forHuman Rights said.Aleppo is divided between government and opposition control, and both rebelbombardments and regime air strikes have intensified in recent weeks.Sunday's mortar fire came as "Islamist rebel brigades blew up a building housingthe Chamber of Industry in the Old City, which was being used as a headquarters bygovernment forces," the Observatory said.There were casualties among the the troops inside the building, it added withoutgiving a precise toll.State television said "terrorist groups have blown up several buildings... includingthe Chamber of Industry."Government aircraft dropped barrel bombs on several opposition-held districts,including Baidine, where six people were killed, the Observatory said.Elsewhere in the country, government troops recaptured a guard post near the townof Samra in Latakia province, the heartland of President Bashar al-Assad's Alawitecommunity, the state SANA news agency said.Fighting was continuing inside the town, which opposition fighters captured last
month, the Observatory said.The UN agency for Palestinian refugees UNRWA meanwhile said it had carried out a
fourth day of aid distribution in the Yarmuk camp in south Damascus after a two-week suspension.The agency said it had delivered parcels to 466 families, noting the "presence oflarge crowds of desperate civilians."There are around 18,000 people in Yarmuk, trapped by a government siege andcontinued clashes between the army and opposition forces inside the camp.