A car in flames at the scene of bombings in the Syrian city of Tartus, northwest of Damascus, on May 23, 2016 (AP)
The death toll from a wave of bombings claimed by the Islamic State group in the heartland of Syrian President Bashar al-Assad's regime has risen to 154, a monitor said on Tuesday.
More than 300 people were also wounded in the Monday attacks in the Mediterranean coastal cities of Jableh and Tartus, some of them critically, the Syrian Observatory for Human Rights said.
Most of the dead were civilians, among them eight children.
The two cities, which are majority Alawite -- the offshoot of Shiite Islam followed by Assad -- had been relatively insulated from Syria's five-year civil war.
The IS group claimed the blasts in a statement, saying they were in retaliation for air strikes by the regime and its Russian ally and threatening "more devastating and bitter attacks".
The Syrian foreign ministry blamed "the regimes of hate and extremism" in Qatar, Saudi Arabia and Turkey, the leading supporters of rebels fighting to overthrow the regime.
More than 270,000 people have been killed since the conflict erupted in 2011. Millions more have been driven from their homes.