Fierce fighting is reported to be taking place in the city of Aleppo in Syria, as rebel fighters try to wrest control from the army.
Pro-government troops are bombarding the city with shells and rocket fire, and there are reports that helicopter gunships are being used.
The BBC reports the offensive began at the weekend. Rebel are claiming control of several areas and are besieging a police headquarters close to the walls of the Old City, which is a world heritage site.
Meanwhile, government forces have already regained control of most areas of Damascus that were captured by rebels last week.
State television has broadcast video of soldiers in heavily shelled suburbs in the south of the capital.