At least 60 people have been killed, including 25 Shi'ite fighters, and dozens wounded by a car bomb and two suicide bombers in a district of Damascus where Syria's holiest Shi'ite shrine is located, a monitor says.
Sunni fundamentalist Islamic State claimed responsibility for the attacks, according to Amaq, a news agency that supports the group. It said two operations "hit the most important stronghold of Shi'ite militias in Damascus".
The Syrian Observatory for Human Rights said the casualties were expected to rise from the suicide attacks in Sayeda Zeinaba, a district of southern Damascus where the Lebanese militant group Hezbollah and other Iraqi and Iranian militias have a strong presence.
Rami Abdulrahman, head of the British-based Observatory, said the suicide bombers had targeted a military bus carrying Shi'ite militias who were changing guard there.
The explosions occurred as representatives of Syria's government and its divided opposition began convening in Geneva for the first UN-mediated peace talks in two years.
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.
State television showed footage of burning buildings and wrecked cars in the neighbourhood.
Syrian state news agency SANA, quoting an interior ministry source, said a group of militants had detonated a car bomb near a public transport garage in the neighbourhood's Koua Sudan area.
Two suicide bombers then blew themselves up nearby as people were being rescued. The authorities put the dead at 45 people.
The area in the south of the city is a site of pilgrimage for Shi'ites from Iran, Lebanon and other parts of the Muslim world.
Syrian Prime Minister Wael al-Halaki was quoted as saying the attacks were prompted by "terror groups" who sought to "raise their morale after a string of defeats" by the army.
The Sayeda Zeinab shrine area witnessed heavy clashes in the first few years of the war but has since been secured by the Syrian army and Shi'ite militias led by Hezbollah, which has set up protective roadblocks around it.
The shrine houses the grave of the daughter of Ali ibn Abi Taleb, the cousin of Prophet Mohammed, whom Shi'ites consider the rightful successor to the prophet. The dispute over the succession led to the major Sunni-Shi'ite schism in Islam.
Iraqi and Iranian Shi'ite militia groups that have volunteered to fight Sunni Islamist radicals in Syria often say they are coming to Syria to defend the shrine.