Syrian government forces have been accused of dropping barrel bombs containing chlorine from choppers on a suburb of Aleppo, injuring 80 individuals.
Volunteer emergency workers say people suffered breathing difficulties on the Sukari area after an assault.
The reports couldn’t be independently verified. An UN led investigation in August found the government had used chlorine .
The Syrian government has consistently denied using chemical weapons.
It comes as Syrian opposition leaders prepare to meet in London on Wednesday to start a new strategy for a political transition to try and stop the battle.
UK Foreign Minister Boris Johnson will, hosts the opposition’s main political group, the High Negotiations
Committee and foreign ministers in the Friends of Syria group will attend.
Saudi Foreign Minister Adel al-Jubeir told the BBC that he still believed in a political solution to the battle, and that Mr Assad wasn’t in a “situation of advantage or success”, despite his forces’ recent progress.
“But if Bashar al-Assad continues to be obstinate and continues to drag his feet and continues to refuse to engage seriously, then obviously there will have to be a Plan B which will involve more stepped up military activity,” he said.