UN observers attended the scene of an alleged massacre in Syria that killed up to 32 children and more than 60 adults near the embattled city of Homs Saturday.
The head of the UN observer team, Gen. Robert Mood, condemned the attack in Houla, northwest of Homs, as a "brutal tragedy" and said team members found artillery tank shells at the site.
He didn't identify who was to blame for the mass killings. Most of the children were under the age of 10.
"It looks as though there was an anti-government demonstration yesterday," CTV Middle East Bureau Chief Martin Seemungal told CTV News Channel Saturday.
"According to the opposition forces, this alleged attack was in retaliation for that, to try and send a message to the people who are challenging the regime," he said in an interview from Jerusalem.
The opposition said government troops shelled the villages before regime militia troops swept through the area, killing people in their homes, he said.
The assault on Houla is one of the bloodiest single events in Syria's 15-month-old uprising.
Former UN secretary-general Kofi Annan is due to visit Syrian President Bashar al-Assad next week in Damascus.
"This appalling and brutal crime involving indiscriminate and disproportionate use of force is a flagrant violation of international law and of the commitments of the Syrian government to cease the use of heavy weapons in population centres and violence in all its forms," Annan and current UN Secretary General Ban Ki-Moon said in a statement.
"Those responsible for perpetrating this crime must be held to account."
Annan helped broker a ceasefire in the country that has largely been ignored by both sides.
"Obviously, his ceasefire that went effect about a month ago is unravelling very quickly, not that it was in very good condition from the beginning," Seemungal said.
"He's going to have a lot of work to do when he gets to Damascus."
Canada's Foreign Affairs Minister John Baird also condemned the violence, calling the killing "very disconcerting because of its depravity."
Baird said the number of children believed to have been killed in Houla is "especially reflective of the regime's utter contempt for humanity and decency."
Activists in the country said the Houla killings appeared to be sectarian, raising fears that Syria's uprising, which started in March 2011 with protests calling for political reform, is edging closer to the type of sectarian war that tore apart Iraq.
The Houla villages are Sunni Muslim. Activists said that the pro-regime forces all came from an arc of villages south of Houla that are populated by Alawites, members of the offshoot of Shiite Islam to which Assad belongs.
"Our area is Sunni and the surrounding villages are Alawite," spokesman Abu Walid said. "I don't like to talk about sectarianism, but it was clear that this was sectarian hatred."
Amateur videos posted online showed dozens of bodies laid out in different rooms, including women wearing Muslim headscarves and children in shorts and T-shirts.
Syrian state TV blamed the "massacre" in Houla on "armed terrorist groups" -- a term it often uses for the opposition.
The London-based Syrian Observatory for Human Rights released an unusually harsh statement, saying Arab nations and the international community were "partners" in the killing "because of their silence about the massacres that the Syrian regime has committed."
U.S. Secretary of State Hillary Rodham Clinton issued a statement Saturday, saying her office condemns the attacks "in the strongest possible terms," and demands that "those who perpetrated this atrocity must be identified and held to account."
The statement went on: "The United States will work with the international community to intensify our pressure on Assad and his cronies, whose rule by murder and fear must come to an end."
The UN has put the death toll at more than 9,000 since the uprising began.
