“The nightmare has become a reality,” Ismail al-Abdullah said breathlessly in a call that came in the dead of the night. “The city of Aleppo has been cut off from the world and we are completely surrounded. We will die here soon, I am sure.”

   Nothing grows here so we haven’t had fruit or vegetables for a week.   

The sound of barrel bombs crashing to the ground could be heard in the distance as Mr Abdullah begged for help.

Some 300,000 residents of the opposition-held eastern side of Syria’s second city are now fully besieged after government forces severed the last route out of the east on Sunday.

Regime fighters descended on the Castello Road, used to bring in produce for residents. Attempting to leave has become a suicide mission with snipers shooting anything that moves.

“Nothing is getting in or out,” said 25-year-old Mr Abdullah, who lives in the northeastern Tariq al-Bab neighbourhood separated from his family on the other side of the city. “Nothing grows here so we haven’t had fruit or vegetables for a week.”

Residents told the Telegraph that there is no more petrol at the pumps and what little food there is left is going for more than four times the normal price.

Umm Wassim Eissa, 40, a teacher from the Sayf al-Dawla district, said: “Usually a kilo of bread is 45 Syrian pounds (15p), now it costs 250. I waited for six hours yesterday to get a few loaves to make sure my family didn’t go hungry.”

“We are hoping that opposition forces will retake the road, but if they don’t manage it soon everyone in Aleppo will starve,” Mr Abdullah said, estimating there were only enough basic supplies to last three more weeks. “That is the regime’s tactic - to starve us to death or into submission.”

“The situation in Aleppo is difficult,” Firas al-Khateeb, the United Nation’s refugee agency (UNHCR) representative in Damascus, told the Telegraph. “We have no access to the city for the time being as the road has become impassable.

“We have no idea if they have provisions or how long it will be before they run out of food.”

President Bashar al-Assad's forces have for years been trying to cut the Castello Road route, in an attempt to raise pressure on rebel forces in the city.

Aleppo, once home to 2.5 million people, has been divided since the summer of 2012, when anti-Assad protests turned into an armed insurrection.

The city is not covered by a nationwide ceasefire, brokered earlier this year by the US and Russia, as the latter claims it is overrun with al-Qaeda-aligned Jabhat al-Nusra jihadists which must be purged.

However, the US-backed Free Syrian Army (FSA), and moderate groups under its banner, say that while Nusra holds part of the outskirts they control most of the city itself.

FSA commanders say the truce has allowed the regime and its Russian and Iranian backers to concentrate on the battle for Aleppo, a city so important to both sides in the conflict that it is often referred to as “Syria’s Stalingrad”.

Attacks on its residents have only become more frequent and more deadly since the ceasefire came into force in February.

Children have since stopped playing in the streets. School lessons are held in underground bunkers, where pupils spend most of their day hiding from warplanes.

Civil defence emergency workers operating in the rebel-held areas say more than 500 people have been killed by Russian and Syrian air strikes on hospitals, mosques and homes in the last month.

Dr Zaher Sahloul, the director of the Syrian-American Medical Society (SAMS), said most of the victims being treated were women and children.

“I saw a 25-year-old pregnant woman who miscarried after a bomb directly hit her house. It killed her son and left her husband brain-damaged, it was devastating,” said Dr Sahloul, who managed to get out of Aleppo two days before the siege.

   That is the regime’s tactic - to starve us to death or into submission.   

“Every single hospital in the east has been bombed. They have started rebuilding them below ground so they can’t be seen and targeted.”

There is now no relief for the small number of remaining doctors, who usually rotate with other physicians outside city.

He said most had enough medicine and surgical equipment to last three-six months “but that’s only if there’s a normal consumption, if air strikes continue at this rate they could run out much quicker.”

Rebels fear the US’s newly agreed “anti-terror” pact with Russia, the regime’s chief backer, to coordinate and intensify attacks against Nusra has all but condemned Aleppo to its fate.

Washington refused to give details of the deal when it was agreed on Friday, but it is believed the outcome may be to effectively support Moscow in shoring up Assad and casts doubt on whether the Americans will come to the FSA’s defence and help break the siege.

“We are preparing for a big battle to open the road, but we will have to do it alone without help from our allies,” Osama Abu Hamza Kenjo, commander of the FSA’s First Regiment, told the paper. “It’s like going into a gun battle with a knife.”

Critics see the offer to aid Russian president Vladimir Putin's campaign in Syria as a victory for the Kremlin's intervention in the country.

“Russia will now be able to claim a counter-terrorism motive for what is obviously a move to starve and defeat a city in revolt against its client regime,” said Kyle Orton, a Middle East analyst at the Henry Jackson society think tank.

“Even when this isn't believed, it will eat time and attention disproving it. All the time, Russia and Assad will be proceeding toward victory.”