Victims of the Houla massacre included dozens of children
Western states have announced they are expelling senior Syrian diplomats following the killing of 108 people in the Houla region of Syria on Friday.
The United States, France, the UK, Germany, Italy, Spain, Canada, Australia, the Netherlands and Switzerland all took action.
Most of the victims in Houla were summarily executed, the UN says.
UN-Arab League envoy Kofi Annan said, after talks with President Bashar al-Assad, Syria was at a "tipping point".
He said he had asked Mr Assad to take "bold steps" to see that his peace plan was implemented.
President Assad blamed the violence on "terrorists". His remarks were quoted by state TV.
Earlier, UN human rights spokesman Rupert Colville said initial investigations had suggested that most of those killed in the village of Taldou, near Houla, were summarily executed.
Comment: Remember this from 2009?
U.S. Rescue May Reach $23.7 Trillion
TARP was nothing more than a heist of gargantuan proportions. Goldman Sachs et al pulled it off against docile Americans when they put a gun to their heads in 2008 and threatened to "pull the economy" if TARP legislation (essentially a TRAP-door through which trillions of dollars was stolen) wasn't passed, but if they think they will get away with a repeat performance against Europe, they've got another thing coming.