Dozens of people were killed at dawn in Douma city to the northeast of the capital Damascus, with both the government and the rebels accusing each other of the massacre.
The state-run SANA News Agency said that an "armed terrorist group has committed an ugly massacre that claimed the lives of 25 people who were killed by knives near Hawa Mosquein Sli Bin Taleb Street in Douma."
The opposition accused the Syrian government of being behind the “massacre".
More top news
The social media firm launched the Online Civil Courage Initiative and plans to educate charities on countering hate speech
The PM told leaders that EU citizens living in Britain for more than five years would be granted the same rights as full British citizens.
Outbreaks of rain across northwestern parts of the UK will move slowly southwards.