Six explosions claimed by the Islamic State group hit government-controlled areas and a province held by a Kurdish militia in Syria on Monday, killing dozens of people, state media and a monitor said.
The blasts took place in the morning in the cities of Homs and Tartous and at the entrance to a town west of Damascus, all held by the government, and in Kurdish-held areas in Qamishli and Hasaka in northeastern Syria.
Islamic State's media outlet Amaq said the attacks were suicide operations targeting the Syrian government and a Kurdish security force. It issued separate statements naming some of the bombers.
Syria's cabinet said the attacks were a response to the recapture on Sunday by the army and its allies of a district of Aleppo that insurgents had seized last month, reinstating a siege on rebel-held parts of the city.
Islamic State is not present in Aleppo, insurgent sources say, but mainstream rebels and hardline Islamist factions both are, including Jabhat Fateh al-Sham, formally affiliated to al Qaeda until it severed ties with the jihadist movement in July.
State television also reported that government jets had struck Islamic State targets near Deir al-Zor, in an area northeast of Damascus and in Suweida province, but without connecting the strikes to the morning's blasts.
The turmoil underlined the complexity of a five-year civil war that has cut Syria into a patchwork of territories held by the state and an often competing array of armed factions and sectarian groups.
Two explosions hit the Arzouna bridge area at the entrance to Tartous, killing 35 people, the Syrian Observatory for Human Rights said, a death toll that was confirmed by the head of a city hospital.
Syrian state television said the first explosion was a car bomb and the second was a suicide belt detonated as rescue workers came to the scene of the first incident.
A car bomb struck the city of Homs at the Bab Tadmur roundabout at the entrance to the al-Zahra neighbourhood, killing three people, state media said.
The Observatory said the Homs explosion hit an army checkpoint, killing four officers.
West of Damascus, there was an explosion at the entrance to the town of al Saboura, along a road which leads onto the Beirut-Damascus highway, killing one person and injuring three, according to a police commander quoted on state television.
A local police chief told state media three men were stopped in a car by security forces.
"The driver was killed and the two others got out of the car and detonated their suicide belts, killing one person," he said.
The Observatory said three people died in the Saboura blast.
A motorbike also exploded in the center of the northeastern city of Hasaka, killing five people including three members of the YPG-affiliated security force known as the Asayish, said the Observatory.
The Kurdish YPG militia, a critical part of the U.S.-backed campaign against Islamic State, took near complete control of Hasaka city in late August after a week of fighting with the government.
The YPG already controls swathes of northern Syria where Kurdish groups have established de facto autonomy since the start of the Syrian war in 2011.
The Observatory said a percussion bomb also went off in the province's city of Qamishli city, but nobody was harmed. Amaq, a news agency affiliated to Islamic State, said seven Kurdish security forces were killed an injured there.