Syrian state media reports claimed on Tuesday that members of the rebel forces have fired chemical weapons in Aleppo province, the BBC reported.
According to the SANA news agency, "Terrorists launched a missile containing chemical products into the region of Khan al-Assal in the province of Aleppo, killing 15 people, mainly civilians", referring to the opposition fighters.
However, rebels denied the claim to the Associated Press news agency.
There have been repeated reports out of Syria that regime forces have used chemical weapons but so far they are unsubstantiated.
According to the Aleppo Media Center, a pro-opposition organization, "poisonous gases" have been fired in the Aleppo area in the north of the country but these were fired by regime forces.