The World Health Organization said Wednesday that 43 of the dead had symptoms “consistent with exposure to highly toxic chemicals.”
The situation "is akin to the day of judgment.”
The London-based Syrian Observatory for Human Rights said Russian warplanes targeted civilian areas around the city's national hospital and other neighborhoods held by a coalition of hardline Islamist rebel groups.
Syrian government airstrikes and shelling by armed groups have killed dozens of civilians in Aleppo over the past few days, and left the cessation of hostilities agreement in tatters.
Government airstrikes and shelling by armed groups have left dozens dead in the war-ravaged city over the past few days, rescue workers and monitoring groups say.
Member States will pool medical teams and equipment to help fight future outbreaks at home and abroad.
As Russian airstrikes continued to pound targets across Syria on Sunday, video footage emerged of volunteer civilian rescuers responding to bombing sites.
Syrians working to save civilians from deadly barrel bombs and alleged chlorine gas attacks again went to the UN to ask for help.