At least 45 people were murdered and 110 wounded on Sunday in three bomb blasts near the revered Shi'ite shrine of Sayyida Zeinab outside the Syrian capital Damascus, state media said.
The attack was claimed by the Islamic State (ISIS) jihadist group shortly afterwards.
State news agency SANA said the first blast was caused by a car bomb that detonated at a bus station near the shrine.
It said two suicide bombers then detonated their explosive belts when people gathered at the scene.
An AFP photographer at the scene said the blasts caused massive damage, shattering windows and ripping a huge crater in the road.
Smoke rose from the twisted carcasses of more than a dozen cars and a bus damaged in the blasts, as ambulances ferried away the wounded and firefighters worked to put out blazes started by the bombings.
The shrine south of the capital contains the grave of a granddaughter of Mohammed, the founder of Islam, and is particularly revered as a pilgrimage site by Shi'ite Muslims.
It has continued to attract pilgrims from Syria and beyond, particularly Shi'ites from Iran, Lebanon, and Iraq, throughout the war, and has been targeted in previous bomb attacks.
In February 2015, two suicide attacks killed four people and wounded 13 at a checkpoint near the shrine.
Also that month, a blast ripped through a bus carrying Lebanese Shi'ite pilgrims headed to Sayyida Zeinab, killing at least nine people, in an attack claimed by Al Qaeda affiliate Nusra Front.
There was no immediate claim of responsibility for Sunday's attack, until ISIS set the record straight.
The area around the shrine is heavily secured with regime checkpoints set up hundreds of meters away to prevent vehicles from getting close to Sayyida Zeinab.
According to the Syrian Observatory for Human Rights, members of the Iran-proxy Shi'ite Hezbollah terror group from Lebanon are among those deployed at the checkpoints.
The Britain-based monitor said 47 people were killed in the blasts, including a car bomb that targeted a checkpoint, and included non-Syrian Shi'ite militants without specifying their nationalities.
Hezbollah is a staunch ally of Syria's President Bashar al-Assad and has dispatched fighters to bolster his troops against the uprising that began in March 2011 with anti-government protests.
Early on, the group justified its intervention in Syria by citing the threat to Sayyida Zeinab.
More than 260,000 people have been killed in Syria's conflict, which has also displaced over half the country's population internally and abroad.
It has evolved into a complex, multi-front war, involving rebels, jihadists, regime and allied forces, Kurds and air strikes by both government ally Russia and a US-led coalition fighting the Islamic State group.
AFP contributed to this report.