BEIRUT — Fierce clashes spread to new neighborhoods in Aleppo in a fourth day of fighting in Syria's commercial capital, showing the resilience of a rebel offensive on strongholds of President Bashar Assad's regime.
President Barack Obama also warned Syria against using its chemical weapons after Damascus acknowledged for the first time on Monday that they possessed such weapons and threatened to use them against any "foreign aggression."
Syria's rebels have recently seized the offensive in the country's bloody civil war, which activists say has killed at least 19,000 people since it began in March 2011. Rebel fighters over the past two weeks have taken the fight to the Assad regime in the country's two largest cities, killed four senior security officials in a bold bomb attack in the heart of the capital and captured a string of border crossings with Iraq and Turkey.
Syria's state news agency said Tuesday that government troops were battling rebels in the Aleppo neighborhoods of Salaheddine and Sukkari and claimed they had inflicted heavy losses. The Britain-based Syria Observatory for Human Rights, meanwhile, reported the spread of fighting to other previously peaceful neighborhoods as well as shelling by regime forces.
Clashes between rebels and government forces spread out of the northeastern neighborhoods of Sukkari and Hanano to nearby areas and even closer to the center in Arkoub. Meanwhile fighting flared in previously quiet southern neighborhood of Firdous.
On Sunday, a newly formed alliance of rebel groups called the Brigade for Unification announced an operation to take Aleppo, the country's largest city with about three million people. While the rebels have not shown themselves able to hold neighborhoods for any significant period of time, the continued fighting highlights the government's inability to pin down the lightly armed opposition forces.
Damascus, which saw an even fiercer rebel assault last week, appears to be largely in government hands once more as regime troops scoured some neighborhoods and shelled others to quash the remaining pockets of rebel fighters.
Syria warned the international community Monday that it had chemical weapons and would use them in the case of any foreign aggression. The regime said it would not use them against its own people.
There had been fears that the embattled regime would use chemical weapons as a final desperate measure against the 17-month old rebellion. But the promise not to use them against Syrians was not entirely reassuring because officials have long characterized the rebels as foreign terrorists.
In a speech before a veterans' association in Reno, Nevada, Obama warned Syria against unleashing its non-conventional arsenal.
"Given the regime's stockpiles of chemical weapons, we will continue to make it clear to Assad and those around him that the world is watching, and that they will be held accountable by the international community and the United States, should they make the tragic mistake of using those weapons," he said.
Israeli Prime Minister Benjamin Netanyahu over the weekend expressed fears that Syria's chemical weapons could fall into the hands of the Iranian-backed militant group Hezbollah. On Tuesday, however, senior Defense Ministry official Amos Gilad asserted that Syria had "complete control" over its unconventional weapons.
Syria has become increasingly isolated on the international stage, with just regional ally Iran in its corner, as well as Russia and China protecting it from condemnation by the U.N. Security Council.
Most of its neighbors, however, have become increasingly hostile, including regional powerhouse Turkey. At a political rally late Monday, Turkish Prime Minister Recep Tayyip Erdogan predicted the imminent end of the regime.
"This regime will go sooner or later. We believe that the people of Syria are ever closer to victory," he said.
Syrian rebel leaders operate on Turkish soil and arms for the opposition are believed to be entering the country from Turkey.
Saudi state TV, meanwhile, announced that the government has collected about $32.5 million in donations as part of a national drive to support "our brothers in Syria." Saudi Arabia has vowed to help fund Syria's opposition movement.