Fifteen people were killed including at least five children in a rocket attack on a market in the northern Syrian city of Al-Bab on Friday, according to emergency responders working in rebel-held areas.
The White Helmets rescue group earlier put the death toll at nine.
It said that figure might rise further as rescue and search operations continued, adding that children were also among at least 30 people wounded in the attack.
The warring factions in Syria's 11-year conflict have carved up the north into a patchwork of zones of control.
Al-Bab falls within the areas of Aleppo province held by the Syrian opposition forces. Other parts are held by the Assad regime troops backed by Russia.
In a statement after Friday's attack, they cancelled the demonstration over fears of further violence.
