Three people were killed by security forces during an overnight protest in a Damascus suburb, ahead of planned mass protests across Syria, activists said on Friday.
The three people were killed when security attacked anti-government demonstrators near the Al-Hassan mosque in Harasta, DPA reported.
Protests have been taking place at night across the country, to allow more people to join after their work and try to avoid heavy security presence.
Security reinforcements arrived in Harasta late Thursday and set up blockades in the main streets. Water, electricity and communications were also cut off, activists said.
More security forces were deployed in both the coastal city of Lattakia and the central Homs.
Pro-democracy activists have called for mass protests on Friday to voice opposition to a "national dialogue" conference proposed by President Bashar al-Assad and set for July 10.
An estimated 1,400 civilians and 348 security personnel have been killed since the protests, calling for al-Assad's ouster, started in mid-March, according to human rights groups.