It was unclear whether the fighting marked the start of a major offensive.
BEIRUT, LEBANON - The Syrian military launched an assault Wednesday on a strategic and highly symbolic rebel stronghold in the northern city of Aleppo, signaling a major government effort to reassert control in the nation's commercial hub.
There were conflicting accounts about which side, if either, had the upper hand.
Syrian state television reported that the government had assumed "full control" over Aleppo's Salahuddin district, the target of weeks of military bombardment.
It reported the deaths of many "terrorists," the government's label for the armed rebels fighting to oust President Bashar Assad.
However, rebel commanders and opposition spokesmen said the battle was ongoing and denied that insurgents had pulled back from Salahuddin.
"Our boys are still there," said Mahmoud Sheik Elzoor, a rebel commander reached by telephone in Turkey. "What the government is saying is not true."
In a video posted online, a commander from the rebel Tawheed Brigade vowed, "We won't leave here till we die."
The frontline neighborhood, parts of which have been reduced to rubble by the bombardment, is both a strategic entry point to Syria's most populous city and a touchstone of the rebellion in Aleppo.
Rebels determined to stay
For months, while much of Aleppo was quiet, Salahuddin was a center of antigovernment protests. Many residents of the working-class district trace their ancestry to nearby rural areas, where opposition to Assad's government is intense.
Most inhabitants have fled Salahuddin since the fighting began almost three weeks ago. Some have escaped to nearby Turkey, joining an exodus that has accelerated in recent days.
The opposition repeatedly has vowed not to abandon Salahuddin.
It was unclear whether the government assault Wednesday represented the army's long-awaited, all-out onslaught or was a limited foray focusing on the Salahuddin area.
On paper, the clash between the two sides appears a mismatch. The government has professional troops, tanks and aircraft at its disposal against ill-trained rebel formations mostly armed with rifles and rocket-propelled grenades. Rebels lack heavy weapons and say they are running low on ammunition.
Salahuddin is in the southwest quadrant of the city, next to the Hamdaniyeh district, where the opposition says scores of government tanks are stationed. On several previous occasions, rebels had reported beating back tank-led attacks on the neighborhood.
Many analysts say Assad cannot afford to lose Aleppo.
"Aleppo means more for the government than it does for the rebels," said Andrew Exum of the Center for a New American Security, a Washington think tank. "The rebels are playing a long game here. They are waging a guerrilla campaign. They don't have to control Aleppo. But the government does."
Talk of no-fly zone
In Washington, President Obama's counterterrorism adviser indicated Wednesday that the administration was studying the possibility of creating a no-fly zone in Syria to prevent airborne attacks on civilians, as well as other steps toward some form of U.S. military involvement.
In an appearance at the Council on Foreign Relations, John Brennan said various options were being looked at "very carefully." Asked if a no-fly zone was under consideration, Brennan said, "I don't recall the president saying that anything was off the table."
In another development, a rebel group calling itself the Hawks Special Operations Battalion said in a video on YouTube that it had "eliminated" Gen. Vladimir Petrovich Kochyev, a Russian military adviser. Russian media said the general was in Moscow.