At least seven Turkey-backed Syrian rebels were killed and 13 injured in Russian strikes on north-western Syria, the Syrian Observatory for Human Rights monitoring group reported on Sunday.
The airstrikes targeted the headquarters of the rebel group in Barad village, in Aleppo province. More victims are expected to be pulled from under the rubble, the observatory added.
Turkey is a main ally of Syrian opposition rebels, while Moscow and Iran back Syrian President Bashar al-Assad in the decade-long war.
The United Nations said that more than 350,000 people have been killed in the conflict in Syria since March 2011, when the uprising-turned-conflict started.
Forces loyal to al-Assad currently control about 70 percent of Syria’s territory, an area home to about 40 percent of the population, the UN said.