Leaders of Syrian rebel forces ordered their fighters to attack hundreds of government troops heading toward the country's largest city, a Free Syrian Army official told CNN Wednesday.
The Syrian regime withdrew about 2,000 fully equipped troops, along with their tanks and artillery, from Idlib and sent them to Aleppo, the official said.
Word of reinforcements in Aleppo came hours after state media reported that regime troops had regained control and mopped up key Damascus neighborhoods where rebels fought President Bashar al-Assad's security forces last week.
ITN journalist Alex Thomson, writing via a blog from Damascus, noted these military strides, saying "it is quite clear that the regime has just had, in Damascus, the biggest boost to its morale in 16 months of violent civil war."
"The crackling of automatic fire, the crumbling explosion of incoming shellfire, the helicopter gunships quartering the city and firing machine gun bursts -- all those sounds have gone pretty much from Damascus today."
"This is a comprehensive victory of the Assad Regime in its own backyard and capital."
But unrest persisted across the country, opposition groups said.
At least 133 people died Tuesday in Syria's violence, including 21 killed during shelling and clashes in Aleppo, the opposition Local Coordination Committees of Syria said.
Rebel forces were working to gain control of Aleppo neighborhoods, activists said.
"There is random shelling of the eastern portion of the city as the Syrian Army is trying to force out the FSA (Free Syrian Army). They are hitting civilian homes over and over," one activist told CNN via Skype.
CNN's Ivan Watson, who is in northern Syria, said he has noticed the rebels have become better armed in the past few months. Where once they only had shotguns, they now have rocket-propelled grenades and assault rifles. The increased firepower has helped the rebels successfully attack armored vehicles and force some Syrian forces to take resupply by helicopter.
The rebels have also been able to establish growing enclaves in northern Syria and from there try to seize a number of key border crossings. Watson said in the village he was in that hundreds of rebels loaded up with ammunition Monday night and headed to fight in Aleppo.
The fighting, spiking for months with the emergence of armed rebels willing to take on the Syrian security apparatus, took an ominous turn this week after a Syrian official discussed his country's weapons of mass destruction.
Jihad Makdissi, Syria's Foreign Ministry spokesman, told reporters Monday that "any stocks of WMD or any unconventional weapon that the Syrian Arab Republic possesses would never be used against civilians or against the Syrian people during this crisis at any circumstances, no matter how the crisis would evolve.
"All the stocks of these weapons that the Syrian Arab Republic possesses are monitored and guarded by the Syrian Army," Makdissi said. He further said the "weapons are meant to be used only and strictly in the event of external aggression against the Syrian Arab Republic."
U.S. President Barack Obama, United Nations Secretary-General Ban Ki-moon and others reacted strongly after the official uttered the threat Monday.
"They will be held accountable by the international community and the United States should they make the tragic mistake of using those weapons," Obama said at a VFW convention.
Russia said Syria has ratified 1925 Geneva protocols "banning the use of asphyxiating, toxic and other gases in military conditions" and expects the country to heed that agreement. That protocol was drawn up and signed "under the auspices of the League of Nations" and "entered into force" in 1928, the United Nations said.
"Russia's policy is based on the understanding that Syrian authorities will continue to strictly follow their international obligations," the Foreign Ministry said. Russia has been a friend and ally of the al-Assad regime.
Ban said Syria is not a party to the Organization for the Prohibition of Chemical Weapons. That's the body of the Chemical Weapons Convention dedicated to eliminating the weapons.
Al-Assad's regime "probably has the largest and most advanced chemical warfare program in the Arab world," according to Michael Eisenstadt, senior fellow and director of the military and security studies program at the Washington Institute for Near East Policy.
It includes "thousands of tube and rocket artillery rounds filled with mustard-type blister agents, thousands of bombs filled with the nerve agents sarin and possibly VX, and binary-type and cluster CW warheads filled with nerve agents for all its major missile systems.
"Its CW infrastructure is believed to include several production facilities and numerous storage sites, mostly dispersed throughout the western half of the country," Eisenstadt said.
Syria is thought to have a biological warfare research and development program but is not known to have offensive biological warfare agents, Eisenstadt told CNN.
Recently, there had been Western intelligence that the stockpiles were being moved.