BEIRUT — A week of intense fighting in Aleppo has left Syria’s largest city reeling. But the worst may be yet to come in the days ahead, with the government and the rebels squaring off in what could be a pivotal showdown.

Aleppo had been quiet for much of Syria’s nearly 17-month-old uprising. In the past month, however, occasional skirmishes and protests have quickly morphed into a raging urban war.

For the rebels, Aleppo offers a tantalizing prize, and one that may be particularly susceptible to their struggle to wrest power from Syrian President Bashar al-Assad. Of Aleppo’s 2.5 million people, a majority are Sunni Muslims, many of whom feel alienated from Assad’s Alawite-led government. The city’s proximity to the Turkish border allows rebel forces to ferry in men and matériel with relative ease.

If the rebels were able to win in Aleppo, they would control a city that has long been Syria’s economic engine, making it even harder for Assad to hang on to power.

“If you take over Aleppo, the march to Damascus becomes much easier,” said Hilal Khashan, a political science professor at the American University of Beirut. “The opposition wants to turn it into a Benghazi,” the city in eastern Libya that became the de-facto rebel capital and expedited the fall of Col. Moammar Gaddafi.

But the government has strongly signaled that it has no intention of allowing that to happen. The military has battered the city with artillery, rocketed neighborhoods with helicopters and, for the first time in the conflict, sent in jets to blast residential areas. The violence is sure to ratchet up: Rebel forces, who claim to control half of the territory in Aleppo, have commandeered tanks and are using heavier weaponry.

The Syrian military blasted parts of the city with artillery shells Friday as fierce street clashes broke out in the Meridien and Furqan neighborhoods. At least six people were killed across Aleppo, according to the Local Coordination Committees, an activist network.

The attacks came one day after the United Nations issued a grim warning. “The focus is now on Aleppo, where there has been a considerable buildup of military means, and where we have reason to believe that the main battle is about to start,” Herve Ladsous, the undersecretary general for peacekeeping operations, said in New York.

In the past week, more than 200,000 people have fled, and thousands more have hunkered down in schools. Dozens have been killed. Those who haven’t left are trapped in their homes and terrified of venturing into the streets.

As a result, many parts of a city that has been continuously inhabited for more than 5,000 years resemble a ghost town. Residents are starving and foraging for food. Stinking mounds of garbage have piled up in streets, sometimes next to corpses. Water is cut most of the day, and fuel and cooking gas are nearly impossible to find.

“Life is like hell,” Mohammed Said, a 25-year-old Aleppo activist, said in a Skype interview. “It’s difficult to survive. You can’t find anything. The government is trying to make a massacre in Aleppo.”