The death toll from a suicide attack in Damascus claimed by Islamic State has risen to more than 70, says the Syrian Observatory for Human Rights.
A car bomb and two suicide bombers attacked the Sayeda Zeinab district, home to Syria's holiest Shi'ite shrine, as representatives of Syria's government and divided opposition began convening in Geneva in an attempt to start the first peace talks in two years on Sunday (local time).
The Syrian state news agency SANA has put the death toll from the co-ordinated attack at more than 50.
Rami Abdulrahman, head of the British-based Observatory, which monitors the war using contacts on the ground, said the attack had targeted a military bus carrying Shi'ite militiamen who were changing guard, and that 42 of the dead were fighters allied to the government.
The Lebanese Shi'ite militant group Hezbollah and other Iraqi and Iranian militias have a strong presence in Sayeda Zeinab, which is a site of pilgrimage for Shi'ites from Iran, Lebanon and other parts of the Muslim world.
While much of the Syrian leadership is drawn from an offshoot of Shi'ite Islam, Islamic State espouses a radical version of Sunni Islam and considers other sects to be heretical.
The area witnessed heavy clashes in the first few years of the war, prompting the army and allied Shi'ite militias to tighten security, notably with roadblocks.
Syrian Ambassador Bashar Jaafari, head of the government delegation at Geneva, said the blasts in Damascus just confirmed the link between what the government says are a Saudi-led and funded Islamist "opposition" and terrorism.