BEIRUT: 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.
Rebels hold most of the eastern side of the city, but regime troops have managed to recapture much of the outskirts surrounding those areas and have been carrying out a relentless aerial campaign across opposition parts of Aleppo province for months.
Opposition forces have attacked regime barracks in the city, and tried to advance into the western Zahra neighbourhood.
They have also cut power lines into the regime-controlled part of the city, where electricity has been out for more than a week.
Sunday's attack came after "Islamist rebel bridges blew up a building housing the Chamber of Industry in the Old City, which was being used as a headquarters by government forces," the Observatory said.
The group reported dead and wounded among soldiers in the building, and said there was fighting ongoing in the area.
State television meanwhile said that "terrorist groups have blown up several building... including the Chamber of Industry."
The Observatory also reported regime aerial bombardment with explosive-packed "barrel bombs" on opposition parts of Aleppo, including in Baidine district, where six people were killed.