A report by Human Rights Watch says the deaths occurred in villages inhabited predominantly by members of President Bashar al-Assad's minority Alawite sect.
It said the findings "strongly suggest" crimes against humanity were committed.
The report names 190 civilians killed by the rebels, including at least 57 women, 18 children and 14 elderly men. The total number of dead is likely higher because many residents remained missing and bodies were buried in mass graves.
http://www.bbc.co.uk/news/world-middle-east-24486627