UN observers witnessed at least 108 bodies in Houla, near Homs, a spokeswoman told CNN. Forty-nine of those were children less than 10 years old.
Some of the dead were killed by "shooting at close range and by severe physical abuse," the Security Council said, without specifying who they held responsible.
According to the Guardian, Russia resisted attempts to blame the point-blank shootings and other violence on pro-government forces. Moscow, traditionally an ally of Syria, maintains that both soldiers and rebels played a part in the violence.
"We are dealing with a situation in which both sides evidently had a hand in the deaths of innocent people," Russian Foreign Minister Sergei Lavrov said at a press conference this morning, cited by the BBC. "Nobody is exonerating the government or the rebels but we must understand how it happened so that it can never be repeated."
Syrian officials have denied all government responsibility for the deaths in Houla, which they blame on "terrorists."
Meanwhile UN-Arab League envoy Kofi Annan has arrived in Damascus, where he is due to hold talks with President Bashar al-Assad tomorrow, Reuters reported.
Admitting that the peace plan he brokered in April had not so far been implemented, Annan urged the Syrian government to take "bold steps to signal that it is serious in its intention to resolve this crisis peacefully, and for everyone involved to help create the right context for a credible political process."