BEIRUT >> Nisrine kept teaching school for months as the siege tightened around the Syrian town of Madaya, but had to give up a few weeks ago when her students got too weak to walk to class. A local medic has been surviving on the rehydration salts he gives patients, while a business school graduate picks grass to make soup for his 70-year-old father, consulting shepherds about which ones their long-since-slaughtered flocks liked best.

The people of Madaya and neighboring Zabadani have tried, since the siege by pro-government forces began in July, to keep society functioning and adjust to their surreal new set of dynamics. There is the black market across blockade lines, for instance, and the quiet or unexpected ways this type of warfare can kill: heart attacks, stillbirths, a step on a land mine while foraging for food.

And there is the relentless physical and psychological contraction of their communities, only an hour’s drive from Damascus, Syria, and two from Beirut yet suddenly sealed off from the outside world.

“I don’t go anywhere,” said Maleka Jabir, 85, who inherited American citizenship from her father, a World War I veteran, and is so disabled from hunger and heart problems she can hardly walk. “I just crumple up and stay in bed.”

Convoys reached Madaya and two nearby towns Thursday, taking basic food, medicine and aid for the second time this week, as Secretary-General Ban Ki-moon of the United Nations declared that “the use of food as a weapon is a war crime” and called on the Syrian government and all warring parties to lift their sieges immediately. Although a limited number of people were evacuated Monday, aid workers say hundreds of people in Madaya remain in acute need: At least 28 have died since Dec. 1, according to Khaled Mohammad, the medical worker surviving on salts, including a 37-year-old man on Wednesday, Ali Awkar, who was from Zabadani and had taken refuge in Madaya.

Hanaa Singer, UNICEF’s top official in Syria, said she was accosted during the aid visit to Madaya on Monday by a woman with six malnourished children.

“She threw herself on me and kissed my shoulder and bent down to my hands,” Singer recalled. “She said: ‘My 17-year-old son died, of hunger. Please keep the rest of them alive.’”

This portrait of life in Madaya is drawn from interviews with more than a dozen residents, conducted over several months and in recent days by telephone and over the Internet; many spoke on the condition that they be identified only by first name, for safety. While details of their experiences could not be independently confirmed, international aid workers who have visited the town or been in direct contact with groups on the ground provided accounts that echoed the residents’.

After nearly five years of civil war in Syria, the United Nations estimates that 400,000 people are trapped behind battle lines by the government, the Islamic State or rival insurgents.

While parts of Homs and the Damascus suburbs have been blockaded for years, Madaya managed to survive relatively unscathed, until last summer.

Madaya and Zabadani lie at the southeastern end of the Qalamoun mountains along Syria’s border with Lebanon. Zabadani, where local rebels took control in 2012, became a haven for insurgents driven from other border areas by Hezbollah, the Lebanese Shiite militia allied with Syria’s president, Bashar Assad.

Both local residents and Hezbollah officials say most of the fighters in Zabadani are affiliated with a Syrian Islamist group called Ahrar al-Sham, and smaller numbers with the more moderate Free Syrian Army and the Qaida-linked Nusra Front.

Weeks of bombardment last summer by Hezbollah did not dislodge the insurgents. Pro-government forces ramped up pressure by cordoning off Zabadani and Madaya, where many civilians from Zabadani — including Nisrine, the teacher — had taken refuge. Looking for leverage, rebels allied with the local insurgents began blockading and bombarding Fouaa and Kfarya, two isolated Shiite towns in Idlib province, in Syria’s northwest.

It worked, partly. A cease-fire was struck in September, but with Russia’s new air campaign in Syria, promises to evacuate the wounded and lift the sieges were never carried out. Madaya residents say the siege tightened instead.

Nisrine stopped getting her salary. Her school was bombarded. She sent her own son to school without breakfast, and students began to lose focus.

“How can I ask him to learn, and he’s hungry?” she said in October.

The medical clinic in Madaya, which works with Doctors Without Borders, was bombed, and thus was moved to a basement. Mohammad, an anesthesia technician who has been acting as a doctor, said he was overwhelmed with cases he could not properly treat: broken bones, amputations, abdominal wounds. He performed primitive C-sections. Lately, he has resorted to giving the most endangered children syrupy medicines, for the glucose, further depleting supplies.

Once, Mohammad said, medics persuaded Hezbollah guards to allow a 16-year-old boy with a bladder infection to leave for treatment.

“We kissed their shoes,” Mohammad said later.

“We’re ready to surrender, but the regime has frozen everything,” he added. “I’m asking Bashar’s regime to launch a rocket and end our lives.”

Hungry women’s breast milk began to dry up. Rima, 25, said her newborn died for lack of an incubator.

“I didn’t feed him, didn’t give him warmth,” she said quietly in an interview days after his death. “I only saw him in a photo.”

Finding food was getting harder. Aid workers and residents said fighters on both sides profited from smuggling it across the lines. There were bribes to cross checkpoints, price-gouging, and regular merchants jacking up prices for scarce supplies. Basic goods could cost $100 a pound.

An anti-government activist named Firas has managed to smuggle in small batches of bulgur wheat that he delivers door to door.

“Oh God, oh God, I hope he’s bringing more,” Samar al-Hussein, 45, a traditional medicine practitioner, said one recent evening as Firas went slowly up her street. A dozen other women, she said by phone, were watching quietly from their doorways.

Firas, though, was in shock. He had taken a meal to the house of Suleiman Fares, 63 and bone-thin, in hopes of saving his life, only to find him already dead. Frustrated, Firas declared that far to the north, rebels allied with those in Madaya ought to resume shelling two pro-government towns — towns full of civilians who are also suffering, tit for tat, a siege from the other side.

“Better to die fighting,” he said that night in one of a series of recent telephone interviews, “than to starve.”

Before Monday, only one shipment of aid had made it through during the siege, on Oct. 18. But half of the high-energy biscuits in that delivery had expired, making some people sick; the U.N. blamed an error in the loading process in Damascus.

The business school graduate, Hamoudi, 27, said his father sometimes refuses to eat, “saving it for us.”

“We don’t eat in the morning. We save the food until evening,” he explained. By food, he referred mainly to water, spices and sometimes grass. “But nowadays there is no more grass,” Hamoudi lamented. “The whole area is covered with snow, and some of the grass is bitter.”

When a donkey was slaughtered, he took home a few ounces of meat, though eating it is prohibited by Islam.

“Starvation is infidel,” he explained. “There is no more halal and haram,” he added, referring to religiously permitted and prohibited foods. “We’re eating everything.”

Finally, in December, a few hundred wounded fighters were evacuated from Zabadani, Fouaa and Kfarya. Nisrine’s husband, Ahmed, was bused from Zabadani to Beirut, then flown to Turkey, and from there shuttled into rebel-held Idlib province.

His wife and 10-year-old son, Abdullah, remained stuck in Madaya. Ahmed, the evacuated fighter, said he recently spoke to the boy.

“I know he’s hungry, but he doesn’t want to say,” the father said in a telephone interview. “Even kids are acting like adults. He no longer asks me to bring sweets — just bread.”

Their neighbors had just slaughtered the last horse in town.

“I know that horse,” Ahmed said wistfully.

“I don’t know what the regime wants,” he added. “We are ready to leave, but they want us to die there.”

Singer, the UNICEF official, said that when she arrived with aid on Monday, crowds of children gathered around her in the dark, pleading, “Auntie, auntie, I’m sorry, I’m so sorry, do you have a piece of bread?”

“That’s what killed me,” she said. “That they were apologizing.”

In the food packs were basics like bulgur and oil, a few pounds per person. But not flour. Or bread.