Airstrikes on a village in the Syrian province of Idlib killed at least 21 civilians on Sunday, among them three children, a monitor said.
The Britain-based Syrian Observatory for Human Rights, which earlier reported an initial toll of 14, said dozens more had been injured in the strikes on the village of Kafr Nabal.
It said the strikes appeared to have been carried out by a Russian warplane.
The Observatory says it determines whose planes carried out raids according to their type, location, flight patterns and the munitions involved.
Hossam Hosber, who witnessed the attack, told AFP “six strikes hit houses and a crowded local market.”
Russia began a military intervention in support of President Bashar Assad in September 2015, saying it was carrying out strikes against “terrorists.”
It denies that its strikes have caused civilians casualties.
In November, Defense Minister Sergei Shoigu said Russian forces had begun a “major operation” targeting Idlib and Homs provinces.
The northern Idlib province is mostly controlled by a powerful rebel alliance known as the Army of Conquest, which groups Islamist factions with jihadists of the Fateh al-Sham Front, al-Qaeda’s Syrian affiliate, which was formerly known as Jabhat al-Nusrah.
Most of Homs province is controlled by the Syrian government, but small parts of the countryside in the region are controlled by a range of rebel groups.
Kafr Nabal gained fame in the early years of Syria’s conflict for the creative, topical and sometimes humorous placards and banners carried by protesters at weekly demonstrations against the government.
More than 300,000 people have been killed in Syria since the conflict began in March 2011 with anti-government protests before spiraling into a complex, multi-front war.