A suicide bomber and a car bomb blew up within minutes of each other at a bus station in the port city of Tartous.
A bus station and a hospital were also among the targets of four bombings in Jableh, a town to the north.
A news agency linked to so-called Islamic State (IS) said the jihadist group was behind the attacks.
Amaq cited an IS source as saying militants had targeted "gatherings of Alawites", a reference to the heterodox Shia sect to which President Bashar al-Assad belongs.
Russia - a key backer of Mr Assad - has a naval base in Tartous and an airbase near Jableh, from where it has conducted air strikes on IS targets across Syria.
The state news agency, Sana, cited a police source as saying that 45 people were killed and many others, most of them women and children, were injured in Jableh.
It reported that two bombs exploded at the main entrance of the town's bus station.
A suicide bomber also blew himself up at the entrance of the emergency department at Jableh National Hospital, it added.
The fourth blast reportedly occurred near the offices of Jableh's electricity directorate, on the outskirts of the Amara residential district.
In Tartous, more than 33 people were killed and 47 injured, Sana said.
A car bomb was detonated at the main gate to the city's bus station, while a suicide bomber detonated an explosive vest inside the facility, it added.
Another bomber blew himself up in a residential area in the west of the city, according to Sana.
The Syrian Observatory for Human Rights, a UK-based monitoring group which relies on a network of sources on the ground, reported that 53 people were killed in Jableh and another 48 in Tartous.
Until now, both Tartous and Jableh had escaped the worst of the five-year war in Syria, which has left more than 250,000 people dead.