Activists say at least 90 people have been killed, including dozens of children, after Syrian government troops pounded the town of Houla in Homs province.
It is the worst violence to hit the country since the start of a UN peace plan.
As well as the shelling on Friday, it is claimed entire families have also been targeted and killed. The reports of violence cannot be independently verified.
According to UK-based opposition group, the Syrian Observatory for Human Rights, residents are continuing to flee, fearing further attacks.
Syrian television said those who have been killed are the victims of a massacre carried out by “terrorist” gangs.
UN observers are reportedly visiting Houla in the wake of the violence. They are in the country to monitor a truce, which has so far failed to stop the violence.