Internet footage has shown hundreds of Syrian rights activists chanting, as scores of wounded and other political prisoners were freed in the centre of the Damascus suburb of Douma.
About 90 people are thought to have been released by secret police who brought them to the square where at least eight protesters were killed on Friday.
Their funerals were attended by thousands. Protesters say they died when security forces opened fire on activists calling for political freedom.
Syria has blamed the violence in Douma and other cities on armed factions.
Opposition groups say at least 60 people have died in recent weeks.
In what appears to be a bid to appease public anger, President Bashar al-Assad has appointed Adel Safar as Syria’s new prime minister. He is charged with forming a new government after Assad accepted the resignation of the old cabinet last Tuesday.