Syrian forces shot dead at least 12 civilians in attacks on pro-democracy protesters after Friday prayers.
They army is also engaged in a military offensive to subdue rebellious towns and to pursue army deserters in the northeast, activists said.
Most of the killings occurred in the countryside around the city of Hama and in Jabal al-Zawiya, a rugged region near Turkey, both scenes of a large armour-backed military operation since last week.
Protesters were also killed on the edge of Damascus, including a 12-year old boy, and in Homs, 165km to the north, they said.
United Nations secretary general Ban Ki-moon yesteray called on President Bashar al-Assad to halt the crackdown on the protests, which began in March.
"For six months, we have seen escalating violence and repression," Mr Ban told reporters at the UN in New York yesterday. "The international community has repeatedly appealed to president Assad to stop, most recently the foreign ministers of the Arab League. He must now listen to such urgent calls."
Agencies