Syrian forces killed at least 63 civilians in attacks to crush pro-democracy demonstrations on Friday.
Thousands of protesters took to the streets after noon prayers on Friday in defiance of security forces determined to crush a revolt against President Bashar al-Assad's 11-year rule.
The Syrian human rights organisation Sawasiah says 53 demonstrators were killed in the city of Hama, and one in the capital, Damascus.
The BBC reports that security forces fired on a crowd of about 50,000 people in Hama, killing at least 53 people but with some accounts putting the death toll at more than 100.
Sawasiah says seven people were killed in the central town of Rastan, which has been under a military assault and a siege by tanks since last weekend.
In the southern city of Deraa, where protests first broke out 11 weeks ago, hundreds defied a military curfew and held protests, chanting "No dialogue with killers", said two of the city's residents.
The protest later broke up.
Syrian forces also opened fire on demonstrations in the eastern city of Deir al-Zor and in Damascus' Barzeh district.
Activists and residents said thousands of people marched in the northwestern province of Idlib, Kurdish northeast, several Damascus suburbs, the cities of Homs and Hama and the towns of Madaya and Zabadani in the west.
Human rights groups say more than 1100 people have been killed in Syria since pro-democracy demonstrations began in mid-March.