Air strikes on Sunday likely to have been carried out by Russian warplanes in Syria's northwestern Idlib province killed 36 people, mostly combatants, the Syrian Observatory for Human Rights said.
"The raids, probably Russian, targeted former regime positions now held by the Army of Conquest," said Observatory chief Rami Abdel Rahman.
AFP reports that the Army of Conquest is a coalition that includes Al-Qaeda's Syrian affiliate Al-Nusra Front and Islamist groups such as its ally Ahrar al-Sham.
"Dozens of people, mostly civilians, were wounded" in the raids, Abdel Rahman added.
Russia began a wave of air strikes on September 30 targeting ISIS and what Moscow calls "terrorist" organizations.
But the West and Syrian rebel movements accuse the Russians of focusing their raids more on groups battling Syrian President Bashar al-Assad's regime.