Syrian rebels in Aleppo have been forced back and restricted to a small area of the city after a series of heavy strikes from pro-government forces, according to a rebel group.

The conflict in the war-torn city in northern Syria will end “in a tragic way” without intervention from foreign nations, and rebels imminently face a “death or surrender” situation, an official from the Jabha Shamiya group said.

He claimed rebels in Aleppo had not received any news about meetings between the US and Russia to resolve the crisis, which has left the city almost “completely destroyed”. He said rebel areas remained full of civilians, many of them unable to escape the conflict.

Syrian government forces have reclaimed large rebel-held areas of the city and have reportedly used chemical weapons to clear out fighters, forcing tens of thousands of people to flee.

Last week, the Syrian army successfully reclaimed the entirety of Aleppo's historic city centre, after months of fighting.

Rebel leaders continue to say they will not give up the city, although they have relinquished almost two-thirds of their territory since the government's assault intensified a fortnight ago.

Officials from the US, UK, Germany and other nations met with the Syrian opposition in Paris on Sunday for fresh talks aimed at ending the conflict.

Foreign minister Boris Johnson accused Bashar Assad's regime of a “flagrant disregard for human life” in its treatment of Aleppo.

In pictures: Aleppo bombing Show all 14 1 /14 In pictures: Aleppo bombing In pictures: Aleppo bombing Bombing in Aleppo Smoke rises after airstrikes on the rebel-held al-Sakhour neighborhood of Aleppo, Syria April 29, 2016. Reuters In pictures: Aleppo bombing Bombing in Aleppo A Syrian family runs for cover amid the rubble of destroyed buildings following a reported air strike on the rebel-held neighbourhood of Al-Qatarji in the northern Syrian city of Aleppo, on April 29, 2016. AFP/Getty Images In pictures: Aleppo bombing Bombing in Aleppo A man reacts as he stands on blood stains at a site hit by airstrikes in the rebel held area of Aleppo's al-Fardous district, Syria, April 29, 2016. Reuters In pictures: Aleppo bombing Bombing in Aleppo The damage of the airstrikes in the rebel-held area of Aleppo on April 28 Reuters In pictures: Aleppo bombing Bombing in Aleppo The damaged the Medecins Sans Frontieres (MSF)-backed al-Quds hospital after it was hit by airstrikes, in a rebel-held area of Syria's Aleppo Reuters In pictures: Aleppo bombing Bombing in Aleppo Syrians evacuate an injured man amid the rubble of destroyed buildings following an air strike on a rebel-held of Aleppo on April 29, 2016. AFP/Getty Images In pictures: Aleppo bombing Bombing in Aleppo People inspect the damage at a site hit by airstrikes, in the rebel-held area of Aleppo's Bustan al-Qasr AP In pictures: Aleppo bombing Bombing in Aleppo A man leads a woman in tears and child out of the scene after airstrikes hit Aleppo AP In pictures: Aleppo bombing Bombing in Aleppo Civil defence members search for survivors after an airstrike at a field hospital in the rebel held area of al-Sukari district of Aleppo Reuters In pictures: Aleppo bombing Bombing in Aleppo A Syrian boy is comforted as he cries next to the body of a relative who died in a reported air strike in the rebel-held neighbourhood of al-Soukour in the northern city of Aleppo Getty Images In pictures: Aleppo bombing Bombing in Aleppo A Syrian family walks amid the rubble of destroyed buildings following a reported air strike in the Bustan al-Qasr rebel-held district of the northern Syrian city of Aleppo Getty Images In pictures: Aleppo bombing Bombing in Aleppo Syrian civil defence volunteers and rescuers remove a baby from under the rubble of a destroyed building following a reported air strike on the rebel-held neighbourhood of al-Kalasa in the northern Syrian city of Aleppo Getty Images In pictures: Aleppo bombing Bombing in Aleppo Syrians help a wounded youth following an air strike on the Fardous rebel held neighbourhood of the northern Syrian city of Aleppo Getty Images In pictures: Aleppo bombing Bombing in Aleppo Syrian civil defence volunteers evacuate people from a damaged building following a reported airstrike in the rebel-held neighbourhood of Tareeq al-Bab in the northern city of Aleppo

“The situation in Aleppo remains dire with desperate images of destruction and a flagrant disregard for human life being splashed across the media on a daily basis,” Mr Johnson said.

“We agreed our first priority must be the protection of civilians and ensuring access for humanitarian aid. It's essential that the regime and its backers provide the United Nations that access with immediate effect.”

Last week, Aleppo council president Brita Haji Hassan said an estimated 800 people have been killed in eastern Aleppo in the past month.