Bulent Kilic / AFP - Getty Images
Syrians run for cover as a helicopter hovers over the northern city of Aleppo on Tuesday.
Syria sent thousands of troops surging toward Aleppo in the early hours of Wednesday, where its forces have been pounding rebel fighters from the air, engulfing the country's largest city in total warfare to put down a revolt.
"[President Bashar] Assad is fighting hard here because he has already lost control of nearly all the towns around Aleppo," NBC News' chief foreign correspondent Richard Engel said from the city's outskirts on Tuesday.
Recent days have seen Syria's 16-month-old uprising transformed from an insurgency in remote provinces into a battle for control of the two main cities, Aleppo and the slightly smaller capital, Damascus, where fighting exploded last week.
President Bashar Assad's forces have launched massive counter assaults in both cities. They appear to have beaten rebels back from neighborhoods in the capital and are turning toward Aleppo, a commercial hub in the north.
Dozens are reported dead in Syria where opposition forces are fighting to maintain control of Syria's commercial capital and biggest city. NBC's Richard Engel reports.
Syrian forces fired artillery and rocket barrages early on Wednesday at the northern Damascus suburb of al-Tel in an attempt to seize the town from rebels, causing mass panic and forcing hundreds of families to flee the area, residents and opposition activists said.
The 216th mechanized battalion headquartered near Tel started bombarding the town of about 100,000 people at 3:15 a.m. (8:15 p.m. ET Tuesday) and initial reports indicated residential apartment blocks were being hit, they said.
"Military helicopters are flying now over the town. People were awakened by the sound of explosions and are running away," Rafe Alam, one of the activists, said by phone from a hill overlooking Tel. "Electricity and telephones have been cut off."
After months of protests and violent crackdowns, a look back at the violence that has overtaken the country.
Some residents said they believed the planes had dropped bombs, but others said booming sounds could have been caused by supersonic jets breaking the sound barrier. A correspondent for Britain's BBC television also said the jets had fired on parts of the city.
Assad's forces have occasionally launched airstrikes from fixed-wing jets on other cities during the uprising, but tend to rely on helicopters for airstrikes in urban areas.
Opposition activists said thousands of troops had withdrawn with their tanks and armored vehicles from the strategic Jabal al-Zawiya highlands in Idlib province near the Turkish border and were headed toward Aleppo.
Rebels attacked the rear of the troops withdrawing from the region at the villages of Orom al-Joz and Rami near the main Aleppo-Latakia road and at the village of al-Bara west of the Aleppo-Damascus highway, activist Abdelrahman Bakran said from the area.
Alex Thomson of Channel 4 Europe reports from Damascus, Syria, where, while at a military hospital this weekend, rebels opened fire disrupting the Syrian Army's ability to carry out funerals for their deceased troops.
"I heard at least 20 rockets fired, I think from helicopters, and also a lot of machine-gun fire," a resident near one of the areas being shelled, who asked to be identified only by his first name Omar, said by telephone.
"Almost everyone has fled in panic, even my family. I have stayed to try to stop the looters; we hear they often come after an area is shelled."
Meanwhile, a Syrian former Brigadier-General spoke for the first time since defecting earlier in July.
In a statement broadcast Arabic news channel Al Arabiya, Manaf Tlas called on Syrians to unite.
AFP - Getty Images, file
An undated photo shows Manaf Tlass smoking a cigar in an undisclosed location.
"I speak to you as a defected member of the Syrian army, who refuses criminal violence … I speak to you as one of the sons of Syria," Tlas said. He was believed to be speaking from Paris where he has family.
"Honorable Syrian army officers do not accept the criminal acts in Syria … Allow me to serve Syria after [President Bashar] al-Assad's era." he said.
Tlas' defection was a significant blow to Assad and his government. While Tlas is from Syria's majority Sunni community -- Assad and much of his inner circle are Alawite, an offshoot of Shiite Islam -- he was reportedly part of the president's inner circle for many years.
"We must all unite to serve Syria and promote stability in the country, rebuilding a free and democratic Syria," Al Arabiya quoted Tlas as saying.
"Allow me to call on a united Syria," he added.
Tlas also said he did not blame those troops who have not defected, adding that "whatever mistakes made by some members of the Syrian Arab Army ... those honorable troops who have not partaken in the killing ... are the extension of the (rebel) Free Syrian Army."
Chemical weapons safe?
Also on Wednesday, Moscow said it had received "firm assurances" from Damascus that its Syrian chemical arsenal is "fully safeguarded," Russian Deputy Foreign Minister Gennady Gatilov told the state-owned Itar-Tass news agency.
"We have received firm assurances from Damascus that the security of this arsenal is fully safeguarded," Gatilov told the agency in an interview.
Syrian Foreign Ministry spokesman Jihad Makdissi acknowledged on Monday that the country had chemical weapons, and Western countries and Israel have expressed fears chemical weapons could fall into the hands of militant groups as Assad's authority erodes.
Government troops launched an offensive against opposition forces in Syria days after rebels killed some of President Assad's top deputies. NBC's Lester Holt reports.
Israel, which has publicly discussed military action to keep Syrian chemical arms or missiles out the hands of Assad's Lebanese militant allies Hezbollah, said there was no sign any such diversion had occurred.
"At the moment, the entire non-conventional weapons system is under the full control of the regime," a senior Israeli defense official, Amos Gilad, told Israel Radio.
Reuters contributed to this report.
More world stories from NBC News:
- Olympic security plan turns London into fortress
- Spain teeters on the edge of a steep 'fiscal cliff'
- Going for gold: British workers cash in on Olympics with strike threats
- Afghan police commander leads defection to Taliban
- After Hong Kong weathers typhoon, anger roils over Beijing flood deaths
- This family's Olympic odyssey includes bikes, satellite dish, reindeer pelts
- In Kenya, cell phones can do everything