At least 65 people apparently shot in the head were found dead with their hands bound in an area of the northern Syrian city of Aleppo, a pro-opposition monitoring group said.
The Britain-based Syrian Observatory for Human Rights said the death toll could rise as high as 80 in what it called a "new massacre".
It was not clear who carried out the killings.
More top news
The mother of "bucket list" cancer patient Stephen Sutton has said signs of her son's illness were "ignored".
Boxing champion and occasional actor Mike Tyson has been praised for coming to the aid of a motorcyclist injured in a crash in Las Vegas.
A website is threatening the release of hacked nude pictures of Emma Watson, reportedly in response to her speech on gender equality.