BEIRUT (AP) -- Syrian government forces mounted new ground attacks against rebel-controlled neighborhoods in Syria's commercial hub of Aleppo, the state media said Monday, but failed to dislodge the opposition from their strongholds, according to activists.
The Syrian army has massed its forces around Aleppo, where rebels hold several neighborhoods after a 10-day offensive, and has been pounding it with tanks and helicopter gunships. There have also been periodic incursions of government tanks but the rebels have held on to their gains.
This use of heavy weapons, particularly helicopters, is just another nail in President Bashar Assad's coffin, U.S. Defense Secretary Leon Panetta said late Sunday during a stopover in Tunisia as he kicked off a Mideast tour expected to focus heavily on the unfolding crisis in Syria.
Already an estimated 200,000 civilians -- almost 10 percent of the population -- have fled the fighting in Aleppo, according to the U.N. official for humanitarian affairs, Valerie Amos, citing the International Committee of the Red Cross and the Syrian Red Crescent. Aleppo is Syria's largest city with around 3 million inhabitants.
Syrian state media reported late Sunday that the army had "purged" Aleppo's southwestern neighborhood of Salaheddine and inflicted "great losses" upon the rebels in one of the first districts they took control of in their bid to seize the city.
There was also a successful operation in Sukhour neighborhood, in the northeast of the city and another rebel stronghold, the state media said.
Activists, however, disputed these claims and just described another day of fierce shelling of certain areas, backed up by the occasional foray on the ground.
"They have tanks in nearby Hamdaniya and there is fighting, and there have been random bombardments of Salaheddine," said Mohammed Saeed, who is based in the embattled city.
While giving no indication that the Obama administration is contemplating military intervention, Panetta said it is increasingly clear that the Syrian crisis is deepening and that Assad is hastening his own demise.
"If they continue this kind of tragic attack on their own people ... I think it ultimately will be a nail in Assad's coffin," Panetta told reporters traveling with him from Washington. "His regime is coming to an end."
Assad's regime has been plagued by a string of defections, including three high ranking diplomats and several military commanders. On Monday, a Turkish official announced that a Syrian brigadier general who was deputy chief of police in Syria's Latakia region, had defected.
The general was among a group of 12 Syrian officers who crossed into Turkey late Sunday, the official said, speaking on condition of anonymity because of Turkish government rules. His defection raises the number of generals to have left for Turkey since the start of the 17-month-old uprising to 28.
But Syria's army remains mostly intact and still vastly outguns the rag-tag rebel army, which is armed for the most part with assault rifles, machine guns and doesn't have the heavy weapons necessary to effectively oppose tanks and helicopter gunships.
The government boosted its forces outside Aleppo and began an assault over the weekend to retake the commercial hub, bombarding rebel neighborhoods and leaving streets littered with rubble and empty apartment blocks with gaping smashed windows, according to videos of the city posted online in recent days.
Fleeing residents described to The Associated Press incessant shelling, shortages of food and gasoline and soaring black market prices for everyday staples.
"I am extremely concerned by the impact of shelling and use of tanks and other heavy weapons on people in Aleppo," Amos said in a statement from New York late Sunday. "Many people have sought temporary shelter in schools and other public buildings in safer areas. They urgently need food, mattresses and blankets, hygiene supplies and drinking water."
She added that while the fighting made getting to the needy very difficult, the U.N. agencies and the Red Crescent were continuing their efforts to deliver food, blankets and hygiene kits.
Associated Press writer Suzan Fraser contributed to this report from Ankara, Turkey.