The initiative was proposed by Russia, President Bashar al-Assad’s most powerful ally, with the support of Turkey and Iran, Assad’s other major ally.
Aleppo is one of the Middle East’s great historic centres, its ancient citadel and mosques, damaged during the ongoing war are a source of Syrian pride.
Syria and its ally Russia, who helped state troops in the retaking of Aleppo have repeatedly denied using chemical weapons.
The fall of Aleppo will only deepen the bloodthirsty sectarianism fuelled by regional powers, who continue to use Syria as a chessboard to further their geopolitical interests.
Some 850,000 of those people are besieged by government forces, the UN said, while the rest are trapped by ISIS militants and other armed groups.
Hundreds of people have been killed since November 15 in a concerted push by the government and its allies to quash resistance in the rebel-held part of Aleppo to re-establish control over Syria’s biggest pre-war city.
The intense bombardment of east Aleppo have created a dire humanitarian crisis, aggravated by frequent air strikes on hospitals and polluted water bodies.
The capture of the base, if confirmed, could be a significant development in the campaign to recapture Mosul, ISIS’s de facto capital
Air strikes blasted neighbourhoods around a children’s hospital and a blood bank in rebel-held eastern Aleppo in a second day of renewed bombing.
Aleppo has become the fiercest front in Syria’s five-and-a-half-year war, pitting President Bashar al-Assad’s forces supported by Russia, Iran and Shi’ite militias against mostly Sunni rebels including some backed by Turkey, the US and Gulf monarchies.
ISIS leader Abu Bakr al-Baghdadi expressed confidence in victory in his first message after US-backed Iraqi forces started an offensive to take back Mosul.
Russia’s defence minister said rebels backed by Western governments had been attacking civilians in Aleppo, despite a pause in Russian and Syrian air attacks.
Rebel groups have launched an assault on western Aleppo in the past few days to try to lift a siege on the eastern half of the city.
The Observatory said at least 38 people including 14 children had been killed in rebel shelling of government-held areas of Aleppo in the last 48 hours.
Russia failed to get re-elected following lobbying by rights groups against Moscow’s candidacy because of its military support for the Syrian government.
The threat of more sanctions on Syria came before a EU summit on Thursday and Friday to discuss sanctions against Russia.
“He was martyred while in hospital as a result of the same bombardment that their house was subjected to,” according to a local council spokesman of Aleppo.
It was the first time Russia has used the territory of another nation, apart from Syria itself, to launch such strikes since the Kremlin launched a bombing campaign to support Syrian President Bashar al-Assad in September last year.