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.”

He said he knows many people who have fled the city. But he feels a responsibility to stay behind and document abuses by government security forces. “I can’t leave,” he said. “I should go inside the city and look in all the areas and see if there is shelling and fighting to send reports.”

Getting the videos and images out isn’t easy, with frequent power and phone outages. But Said has a powerful tool: a satellite modem. When the electricity comes on even briefly, he sends out whatever information he can.

The dangers involved with his work are obvious. An activist friend was shot by a sniper three weeks ago. The family received his mutilated body from security forces only last week.

Many residents are still stunned by how rapidly the fighting spread across the city. “I was extremely surprised when the situation escalated so fast in Aleppo. One day I’m going to my work and hearing about fights around Syria,” said a 28-year-old man who asked not to be identified for safety reasons. “The next I’m hiding home in my bathroom with my family while my little niece is crying her heart out to the sounds of bombs.”

The area hit hardest by the fighting has been Salahuddin, a hard­scrabble neighborhood of mostly working-class Sunnis in southwest Aleppo. The neighborhood is full of opposition supporters and is next to the Al Assad military academy. Each time soldiers leave the base to travel to the city center, they pass through Salahuddin, kicking off fierce clashes with rebel fighters, according to opposition activists. In the past week, the military has pounded Salahuddin with artillery.

“The fight in Aleppo is a matter of life or death for both the opposition and the regime,” Abu Thabet, a Free Syrian Army commander in Salahuddin, said in a phone interview. “We have military plans and determination. The regime has superior weapons, but we are stronger in street-fighting tactics inside the cities.”

Rebel forces have been able to hold territory for longer periods in Aleppo than they have in other cities, and in the areas they control, they have occasionally distributed food and fuel.

Still, there are residents of Aleppo, like those in the predominantly Christian Sulaimaniyah district near the city center, who fear the rebel fighters. Yekso, a 40-year-old mother of two who is an Armenian Christian, said she and her family barely leave the house. Her husband owns a spare-parts store, but he hasn’t opened the shop in more than 10 days. They have primarily relied on donations of bread and water from a local Armenian club for their survival.

Earlier this week, she watched, terrified, as rebel fighters planted bombs in the streets around her neighborhood. It took the army several hours to dismantle the bombs the next day. “We are very afraid that the Free Syrian Army will come out in the streets and we get caught in the middle of the fighting,” she said.

Other Christians in Aleppo said they fear radical Islamist fighters within the opposition.

As the fighting intensifies in Aleppo, analysts say, sectarian enclaves are likely to develop. The worst-case scenario would be a complete reshuffling of the demographic makeup of the city, which happened during the height of the sectarian violence in Baghdad in 2006 and 2007.

A government defeat in Aleppo still may not signal the end of Assad. “Even if Assad loses Damascus and Aleppo, he’ll flee to the coast among the Alawites,” said Khashan, the AUB professor. “He’ll become a militia leader.”

Ahmed Ramadan and Suzan Haidamous contributed to this report.