Activists and witnesses in Syria say security forces have used live ammunition and tear gas against protesters in several cities.

Thousands of anti-government demonstrators poured into the streets following Friday prayers, and there are reports of at least three deaths.

Activists had urged citizens to protest against the imprisonment of hundreds of people in the government's crackdown on pro-democracy protesters.

The call to protest comes a day after Syrian rights activists said government forces had killed six people and arrested more than 20 others across the nation since Wednesday.

There was no independent confirmation of the casualties. Syria does not allow foreign media into flashpoint areas.

Syrian President Bashar al-Assad has been trying to crush a four-month old opposition uprising against his 11-year autocratic rule.

He also has made promises of political reforms, but opposition groups have dismissed the offers and demanded an end to the deadly crackdown on their movement.