Activists say the violence Tuesday included heavy fighting in several neighborhoods. They also reported an attack by government forces on the city's central prison that killed at least eight detainees.
The opposition Local Coordination Committee said government forces Tuesday were also shelling areas outside of the capital, Damascus, as well as Deir Ezzor and Homs.
Meanwhile, U.S. President Barack Obama joined other world leaders in warning Syria against using chemical weapons. Obama said Monday that Assad would be held accountable if Syria used poison gas or other deadly chemicals.
His comments came after Syrian Foreign Ministry spokesman Jihad Makdissi said the government would never use chemical weapons against its own people, but would unleash them against what he called foreign invaders. He said the military is securely guarding the nation's weapons stockpile.
U.N. Secretary-General Ban Ki-moon said Monday that it would be "reprehensible" for Syria to consider using weapons of mass destruction such as chemical weapons. He said he hopes the international community monitors the situation to ensure such an attack does not happen.
