Syrian activists say more than 90 people have been killed by artillery fire over the past 24 hours in the town of Houla in the central Homs province.
Footage has emerged on YouTube
purportedly showing the bodies of dozens of children killed in Houla since government troops began shelling the town on May 25.
The reports could not be verified because of restrictions on foreign media.
But if the death toll is confirmed, it would be one of the highest for any single incident since the popular uprising against President Bashar al-Assad's regime began in March 2011.
The United Nations said a team of UN observers was heading to the area.
The UN says more than 10,000 people have been killed in Syria since the violent uprising began last year.
The violence has continued despite a UN-brokered truce and the presence of UN observers.
Based on reporting by Reuters, AP, and AFP