Two suicide attacks, claimed by the Islamic State extremist militia, rocked a mainly Shiite suburb of the Syrian capital Damascus on Saturday, killing at least 20 people, a monitoring group said.
The Syrian Observatory for Human Rights said the synchronized attacks occurred in Damascus' southern area of Sayeda Zeinab, home to a shrine revered by Shiite Muslims.
At least 30 people were wounded in the explosions caused by a car bomb and a suicide attacker wearing an explosive belt, the watchdog said.
Syria's state-run news agency SANA put the death toll for the twin arracks at 12 people, with 55 injured, including children.
Syrian Prime Minister Wael al-Halqi blamed the "monstrous massacres" on Turkey, Saudi Arabia and Qatar, in comments carried by SANA.
The three countries are staunch supporters of rebels seeking to oust Syrian President Bashar al-Assad.
Syrian television showed footage of heavy damage and vehicles ablaze on the scene.
Islamic State's Aamaq news agency said that the attacks had been carried out by the jihadist group. It claimed there had also been a second suicide attacker, but that was not supported by other accounts.
The Sayeda Zeinab shrine, which is around 10 kilometres south of Damascus, is heavily guarded by pro-government forces and their allies from the Lebanese Shiite Hezbollah movement, according to local residents.
The suburb has seen several bomb attacks claimed by Islamic State - which considers Shiites to be heretics - in recent months.
The worst such attacks, in February, killed 134 people, according to the watchdog.
The al-Qaeda splinter group is increasingly under military pressure elsewhere in Syria.
US-backed Arab and Kurdish fighters are imposing a tight siege on the Islamic State-held city of Minbij in northern Syria.
The blockade has trapped tens of thousands of civilians there, the watchdog warned.
"More than 200,000 people are estimated to be inside the besieged town," Syrian Observatory head Rami Abdel-Rahman said.
"We have fears that Islamic State will use those civilians as human shields," he told dpa.
The Democratic Forces of Syria (DSF), a group dominated by Kurds but containing large Arab contingents, are now set to start a major offensive to enter Minbij, which has an estimated 2,000 Islamic State fighters inside it, according to a number of activists in northern Syria who declined to be named.
On May 31, the DSF started an onslaught to seize Minbij, which has been under Islamic State control since 2014.
The watchdog said heavy fighting backed by strikes by the US-led coalition continued mainly southwest of Minbij, with the DSF pushing towards the city of al-Bab only 18 kilometers away.
According to the watchdog, the forces aimed to cut off the strategic road between al-Bab and Turkey and thereby "end the link between the Islamic State and the outside world," the watchdog said.
Capturing al-Bab would also be key to the long-standing Kurdish aspiration of linking their main territory along the Turkish border with the north-western Efrin enclave.
Turkey is deeply opposed to such Kurdish expansion, partly because the dominant Kurdish Democratic Union Party is closely linked to Kurdistan Workers Party (PKK) rebels operating inside Turkey.
Meanwhile, in central Syria a new convoy of aid including food for over 14,000 families entered the besieged area of al-Houleh, north of Homs, the International Committee of the Red Cross said.
The aid, the first to reach the area since March, was allowed through two days after UN Syria envoy, Staffan de Mistura, announced that the Syrian government had agreed to permit aid convoys into several besieged areas.
According to the UN, an estimated 492,000 people live in 19 areas under forms of siege. 16 of those are rebel-held areas besieged by government forces, while three are controlled by the government and besieged by rebels or Islamic State.
Last month the main international power brokers demanded more access for humanitarian goods in Syria, saying they would push for airlifts into besieged area if there was no progress on aid shipments on the ground.