Mohib Abdelsalam, 26, a rebel fighter and volunteer first responder in his home town of Aleppo, Syria, says conditions in opposition-held areas of the city have grown more dire this summer. (Courtesy of Mohib Abdelsalam)

The past four years have been hell for Aleppo native Mohib Abdelsalam, as Syria’s civil war left thousands dead and reduced entire neighborhoods to rubble in opposition-held areas of his home town.

But this summer, the 26-year-old rebel said, life got even worse. A burst of intensified fighting has rocked the flash-point northern city, long divided between rebel districts in the east and government-controlled areas in the west. The 300,000 residents of the eastern enclaves suddenly faced a punishing siege and worsening shortages of food, water and drugs amid a surge in attacks by government and Russian fighter jets.

For Abdelsalam, an emergency responder who lost four family members to a bombing in June, the horrors have become almost unbearable.

“You don’t understand,” he said, speaking via Skype. “Now it’s like any kind of day-to-day life is impossible.”

The ongoing fighting appears to be building into an important battle in Aleppo, Syria’s largest city before conflict erupted five years ago, killing 400,000 people across the country and displacing millions.

A Syrian man covered with dust carries pieces of metal on a street cluttered with rubble after a reported airstrike on the rebel-held Aleppo neighborhood of Sakhur on Monday. (Ameer Alhalbi/AFP/Getty Images)

Winning control of the entire city is a goal that has eluded both sides since rebel forces stormed it in 2012, and the fierceness of this summer’s battles underscores how much both still see it as a potential game-changer in the war. For residents, though, the stakes are more immediate — and measured in daily suffering.

Rebel fighters this month managed to partially lift the government blockade of their strongholds in the city. Now those fighters — some of them linked to al-Qaeda — are expanding their offensive to shell and besiege government-run neighborhoods, which are also experiencing water and food shortages.

Meanwhile, Shiite militants from Iran, Lebanon, Iraq and Afghanistan have led the pro-government counterattacks against the eastern areas, while Syrian and Russian planes target hospitals and just about anything that moves there, including cars and people walking to the market, residents say.

“There’s no mercy from the sky,” said Issam Ghazal, a 50-year-old resident of the eastern district of al-Zeydiya.

The situation has prompted dire warnings from aid groups and U.N. officials.

“In Aleppo, we risk seeing a humanitarian catastrophe unprecedented in the over five years of bloodshed and suffering in the Syrian conflict,” U.N. Secretary General Ban Ki-moon said Tuesday.

The stunned and wounded 5-year-old boy in Aleppo, Syria, has been treated for his wounds, but the trauma will stay with him and his family for years with few treatment options in the war-torn city. The Post's Max Bearak spoke with a doctor who has worked in one of the few remaining hospitals in Aleppo. (Jason Aldag/The Washington Post)

Such distant expressions of concern mean little to Abdelsalam. He feels as if the rest of the world has left him to deal alone with catastrophes like the one that engulfed his family on June 23, about the time forces loyal to Syrian President Bashar al-Assad were beginning their attempt to cement the encirclement of eastern Aleppo.

At about 8 a.m. that day, Abdelsalam said, he received a phone call telling him to rush to his family home in the Meyesr neighborhood. A rocket had smashed into it, and casualties were likely, the caller said.

When he arrived, he saw nothing but rubble where the building he had grown up in had stood. Under it lay the bodies of his sister-in-law, 35-year-old Samar, and her three children: Abdelsalam, 13, Ahmed, 11, and Aya, 9.

“I just remember seeing them dead, and then waking up on the ground. I passed out. It was too much,” Abdelsalam said.

He, nevertheless, pulled himself together and helped retrieve the bodies. During the conflict, he said, he had developed strong nerves while volunteering as a first responder during scores of similar incidents in the rebel-controlled part of the city.

What he cannot forget, though, he said, is the sight of his 40-year-old brother Mohammed, who somehow emerged unscathed from the rubble. Mohammed, an elementary-school Arabic teacher before the war, just stood there, Abdelsalam recalled, as he watched a scrum of shouting men pick through concrete and rebar to pry out his wife and children, whose crushed, limp bodies were smeared with dust and blood.

“He didn’t talk. He didn’t move,” Abdelsalam said. “He just stood there in disbelief.”

Shortly after that, in early July, government forces cut off the main supply road to eastern Aleppo and imposed a blockade on the area. People began running out of food, Abdelsalam recalled, hoarding all they could.

Abdelsalam began restricting his meals to a piece of bread, cheese and, if he could get it, canned tuna. Fruit and vegetables all but vanished.

The siege has had a traumatizing effect, he said. He recalled seeing one woman, a mother who had recently lost her husband during a bombing, using paper scraps and pieces of wood to bring a pan to boil in the middle of the street. Her three young children sat around her as she prepared what he thought was a meal.

“But when I looked at what she was boiling, it was just water,” he said. “It was like she was pretending that she was cooking food for her kids, but she wasn’t pretending.”

Before the war, Abdelsalam worked repairing computers and cellphones. As the peaceful uprising of 2011 turned into armed conflict, he said, he felt compelled to help the rebellion drive government forces out of Aleppo.

During the war years, he has regularly posted on his Facebook page video footage captured on his cellphone of the aftermath of government air raids. From time to time, he said, he has fought alongside various rebel groups in the city.

One such time was earlier this month, when he said he helped fellow rebels launch a surprise offensive to break the siege of eastern Aleppo. He has also worked since to bring in food, medicine and fuel from rebel-held Idlib province to the west.

It is a dangerous journey, he said, with Russian and government aircraft targeting anything that seems to be moving in and out of rebel parts of Aleppo. He takes obscure routes, driving at night with headlights turned off to avoid detection.

“We call it the way of death,” he said.

But it is the only way to bring sustenance to rebel areas of Aleppo. A few days ago, a rocket exploded near the Ford Explorer he was riding in. The vehicle was destroyed, but he and the other passenger were not injured, he said.

Abdelsalam does not expect such luck to continue. But, he said, he must continue with the dangerous missions so that desperate residents can eat.

“It’s either we fight the regime and win, or we die trying,” he said.

Heba Habib in Stockholm, Zakaria Zakaria in Istanbul and Louisa Loveluck in Washington contributed to this report.