Syrian security forces killed at least seven people after thousands of protesters took to the streets, activists say.
The protesters claimed President Bashar Assad never intended to keep to an Arab League plan to end violence.
The bloodshed was a blow to the 22-nation Arab League, which announced on Wednesday that Damascus agreed to a broad plan that included an end to violence against demonstrators.
Opposition groups called for a large turnout in yesterday’s protests to test whether the regime would refrain from using deadly force.
Gunfire erupted shortly after the protests began, in the same pattern as previous Fridays for months.
“This regime is not serious about ending its brutal crackdown,” said Mustafa Osso, a Syria-based human rights lawyer. “Today was a real test for the intentions of the regime and the answer is clear to everyone who wants to see.”
Thousands of protesters braved cold and rainy weather to stage anti-Assad demonstrations.
Most opposition leaders refuse to meet Mr Assad because of his brutal crackdown, which has cost about 3,000 lives in nearly eight months of protests, according to the UN. Instead, protesters demand that he resign.
Activists said the deaths yesterday came in the city of Homs, which came under heavy bombardment on Thursday, and suburbs of the Syrian capital.
A resident of Homs said mass marches formed after Friday prayers in most districts of the city, despite the heavy security presence and violence of the past days.
Mr Assad, 46, still has a firm grip on power, in part because he has the support of the business classes and minority groups who feel vulnerable in an overwhelmingly Sunni nation.
Also, he appears to retain the backing of most of the military, despite some defections.