Air strikes on a camp in northwest Syria run by rebel fighters backed by Turkey killed at least 35 people and wounded scores on Monday, a war monitor and a rebel source said.
The rebel source said suspected Russian strikes targeted the Failaq al-Sham faction in their base close to the border with Turkey, killing 35 and injuring 50 others. Many remained missing, the source said.
There was no immediate comment from Moscow.
The UK-based Syrian Observatory for Human Rights put the death toll at 78, with scores wounded.