At least 18 people were killed and 15 others wounded on Sunday when a suicide bombing struck an eastern district of Damascus, a monitor said.
"Nine were killed, among them civilians and soldiers, in the suicide bombing that hit Tahrir Square in Damascus," Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, told AFP.
Three car bombs exploded in Damascus on Sunday, killing and wounding a number of people, state media reported.
One of the suicide bombers blew himself up in a square in central Damascus after being encircled by the authorities. The other two car bombs were destroyed by the authorities, state media said.
State TV said the security forces had prevented "the terrorists from reaching their targets", saying they had aimed to target busy areas on the first day back to work after the Eid al-Fitr holiday.
Footage broadcast by state TV from one of the blast sites showed what appeared to be human remains, badly damaged vehicles outside a mosque in the Baytara traffic circle near the Old City.