Both sides in the Syrian conflict have blamed the other for firing a chemical weapon at a village killing 16 people.
Syria’s information minister said it was the “first act” by the opposition interim government.
Omran al-Zoubi said the missile containing “poisonous gases” was fired from Nairab district in the town Aleppo into Khan al-Assal village.
He said 16 people were killed and 86 wounded in the attack.
He added the attack was the result of the decision by some in the international community to arm the Syrian opposition.
Rebels have denied the accusation and say regime forces fired the missile.
If the attack is confirmed, it would mark the first time chemical weapons have been used since the uprising against president Bashar Assad began in March 2011.
One of the international community’s top concerns since fighting began is that Syria’s vast arsenal of chemical weapons could be used by one side or the other or could fall into the hands of foreign jihadist fighters among the rebels or the Lebanese militant group Hezbollah, which is allied with the regime.
The reported attack was in an area just east of Aleppo that had seen fierce fighting for weeks before rebels took over a sprawling government complex there last month.
The facility included several military posts and a police academy that Assad’s forces have turned into a military base that regularly fires shells at nearby villages.
Syria’s opposition coalition earlier elected a little-known American-educated IT manager to head an interim government to administer areas seized by rebel forces from Assad’s troops.
In his first speech after his election, Ghassan Hitto ruled out dialogue with the regime.
He said the interim government will be headquartered in rebel-held territories in northern Syria and urged international recognition for the new entity.
As rebels make gather momentum with the capture of military bases and other strategic sites, concerns have mounted over the security of the chemical weapons arsenal.