The Britain-based Syrian Observatory for Human Rights said 18 people were killed in the airstrikes on the road between the villages of Ratla and Kasrat.
It said today's airstrikes hit buses, adding that the identity of the dead is not known.
The activist-operated Raqqa is Being Slaughtered Silently said 17 civilians were killed in the airstrike on buses carrying civilians.
Both groups blamed the US-led coalition, which has been carrying out airstrikes in Syria against IS since September 2014.
Disclaimer: No Business Standard Journalist was involved in creation of this content