Four attacks took place within an hour in Tartous, Homs and in a suburb of Damascus, with one in Hassakeh, which is dominated by Kurdish forces.At least 40 people have been killed in bombings in mainly government-held areas of Syria, state media report.
The deadliest incident was outside Tartous, home to a Russian naval base and in the heartland of President Bashar al-Assad's Alawite sect.
The Islamic State (IS) group said it was behind the attacks.