Daesh (ISIL) terrorist group claimed responsibility for the attacks in the Mediterranean cites that have up to now escaped the worst of the conflict, saying it was targeting supporters of Syrian president Bashar al-Assad.
Scores were wounded in at least five suicide attacks and two car bombs, the Syrian Observatory for Human Rights said, the first assaults of their kind in Tartous, where government ally Russia maintains a naval facility, and Jableh.
State media confirmed the attacks but gave a lower toll, according to Reuters.
State media reported that a car bomb and two suicide bombers attacked a petrol station in Tartous. In Jableh, one of the four blasts hit near a hospital, state media and the Observatory reported.
Footage broadcast by the state-run Ikhbariya news channel of scenes of the blasts in Jableh showed several twisted and incinerated cars and minivans.
Pictures circulated by social media users showed dead bodies in the back of pick-up vans and charred body parts on the ground.
Bombings in the capital Damascus and western city Homs earlier this year killed scores and were claimed by Daesh.
Syria has been gripped by foreign-backed militancy since March 2011. UN Special Envoy for Syria Staffan de Mistura estimates that over 400,000 people have been killed in the conflict, which has furthermore displaced over half of Syria’s pre-war population of about 23 million.