Hundreds of thousands of residents in the besieged Syrian city of Aleppo are shunning so-called “humanitarian corridors” set up by Russian and Syrian forces, choosing to risk starvation and an escalating campaign of airstrikes rather than leave their homes and trust their lives to the attacking armies.

Just 169 civilians have left the city through the corridors since Friday, Russian military forces said in a statement quoted by AP, and 69 fighters have laid down their arms. There are estimated to be more than 300,000 people still in the city, according to councils and aid groups working there.

Few people in Aleppo believe guarantees of safe passage from a government that has for years bombed civilian targets including hospitals, markets and schools, says American-Syrian doctor Zaher Sahloul, who left the city days before it was totally cut off.

“How can you trust a government that is bombing you every day? I am not talking about bombing fighters, I am talking about bombing children and hospitals,” said Sahloul, who has visited Aleppo several times as a volunteer medic over the past four years. “But they are the same people who are saying ‘you can come out safely’.”

The plan has already had a frosty reception from western powers, with US secretary of state John Kerry sharing concerns that the offer could be a “ruse”. The UN envoy for Syria has snubbed Russia by describing the creation of humanitarian corridors as “our job”. “How do you expect people to walk through a corridor, thousands of them, while there is shelling, bombing, fighting?” Staffan de Mistura said.

The agony of families trapped in Aleppo, as the battle for the city intensifies, is captured in one photo of four young sisters from the Hamami family lying on makeshift beds of cushions and blankets inside a bathroom. The picture, taken by an uncle, captures a scene repeated around the city, as desperate parents look for safe places from airstrikes and the shrapnel they unleash.

“Most of the families let their children sleep either in the bathroom or a basement, even when they are not fit for a human to stay in, because they feel that they can be protected better in these places,” Sahloul said.

He visited an orphanage where 40 children tried to entertain their guests by putting on a show, but with a subject as dark as any Shakespearean tragedy.

“They did a play for us talking about the coming siege, and how they are scared they will have to eat grass and cat meat like the people in Madaya,” Sahloul said, referring to another city besieged by government forces, where dozens of people have starved to death.

Everyone still in Aleppo knows they face long months of hunger and suffering, he says, but they fear the “humanitarian corridors” offer even grimmer prospects, for several reasons.

People try to remove their belongings after Russian airstrikes. Photograph: Anadolu Agency/Getty Images

Some are terrified they will be gunned down by government snipers if they try to use the corridors. Marksmen regularly picked off civilians trying to cross between government and rebel-held areas earlier in the war, and there are reports they have already tried to target people crossing now, Sahloul said.

Others are more afraid, if they did safely cross to government-controlled areas, of the reception they would get from a regime known to torture, murder and “disappear” its opponents.

“They have been living there three or four years and don’t dare leave, because they fear the government will treat them as ‘terrorists’,” Sahloul said, adding that for young men there is an additional worry that if they are not labelled enemies of the state, they could be drafted to fight for it.

Many also believe the offer of refuge is just cover for plans to permanently remove them. “Many believe it’s forced ethnic cleansing, that it is to change the demographic and force people out of their homes,” he said.

That concern is echoed by US officials, who privately admit they fear the Syrian government may want to depopulate the city to ease a final assault, Reuters reported. “Why would you evacuate a city you wanted to send humanitarian aid to?” one official said.

Inside the city, food prices have tripled, bread is beginning to run out in some areas and vegetables are disappearing from markets, Sahloul said.

For now families, doctors and charities are all relying on supplies stockpiled as the threat of siege, which has hung over the city for years, draws closer. But doctors are bracing for the first signs of malnutrition among the most vulnerable children and older people, as not every family could afford to get in supplies to last months.

There are also concerns about medical supplies, which were built up to last for several months but are being used up rapidly because of the intensity of the bombing – even as schools, hospitals and much of life in the city moves underground in a bid to avoid the air campaign.

The severing of the last road out of Aleppo has also pushed up demand for beds, because the most serious cases can no longer be evacuated, and so the wards are constantly filled to overflowing and doctors face heartbreaking decisions about triaging patients.

Sahloul warns that the size of Aleppo, and its historic importance, means that the collapse of rebel-held areas would not just carry the risk of a humanitarian tragedy, but also present security threats to the west.

“If Aleppo falls, it will be portrayed as a betrayal by the international community of Syrians, and there will be people who try to use that,” he warned. “The same pictures you see are used by Isis and other groups for recruiting.”