EDITED BY KALAHAN DENG
Two teams of suicide attackers launched coordinated assaults on Monday deep inside Syrian government territory, killing scores of people in a relatively secure region where support for President Bashar al-Assad runs high.
Amaq, a news agency that is associated with the Islamic State, said jihadists from the militant group had carried out the attacks to strike “groupings of Alawites,” the religious sect of PresidentAssad.
But the attacks, on bus stations and the emergency department of a public hospital, seemed to target civilians in a religiously diverse area whose population has doubled as Syrians from elsewhere in the country have sought refuge from violence in their own communities.
The attacks also appeared to reflect the changing tactics of the Islamic State as its military fortunes have dimmed. Having lost significant territory from their self-declared caliphate in Syria and Iraq, they have turned their focus to external expansion while stepping up suicide bombings against civilian targets in places like Baghdad.
The assaults were also a blow to Mr. Assad, who has portrayed his government as a bulwark against terrorism.
Merely pulling off the bombings was a logistical feat that calls into question the effectiveness of Syria’s defenses. To reach the areas attacked, the jihadists would have had to move large quantities of explosives and a group of militants across more than 30 miles of government-controlled territory without being detected, suggesting a major security breach. Another possibility was that the militants had organized the attacks and built their bombs locally — an even scarier prospect for residents of the area.
The attacks shattered the relative calm in two cities, Jableh and Tartus, both on Syria’s Mediterranean coast, a region where support for Mr. Assad remains strong and where militant attacks and rebel activity have been rare. While the concentration of Alawites is high, the area also has large populations of Christians and other Muslims.
Russia, which backs Mr. Assad and has supported his troops with airstrikes and other military aid, has a naval base in Tartus and an air base nearby.
A spokesman for President Vladimir V. Putin of Russia said on Monday that a recent surge in militant attacks and bombings, “once again demonstrates how fragile the situation in Syria is.”
Asked whether Russia would reconsider its decision to scale back the size of its military contingent in Syria, the spokesman, Dmitri S. Peskov, cited a previous statement by Mr. Putin that Russia’s bases in Syria allowed for “a very flexible approach” to its deployments.
The Syrian state news agency, SANA, and the Syrian Observatory for Human Rights, which opposes the government and tracks the conflict from Britain through contacts on the ground, described the attacks as coordinated and intended to maximize civilian casualties.
In Jableh, two blasts struck the bus station, then suicide attackers blew themselves up near an electricity administration building and at the entrance to the emergency department of a hospital.
In Tartus, a car bomb hit the bus station, then two suicide bombers targeted people who had gathered in the aftermath.
SANA said that at least 78 people had been killed in the two attacks. The Observatory reported at least 121 dead and many more wounded.