The death toll from twin bombs targeting Shia pilgrims visiting a pilgrimage site in Damascus has climbed to 74, the Syrian Observatory for Human Rights reported on Sunday, with over 100 people wounded in the attacks.

Most of the dead in Saturday's attack were Iraqi Shias who were going to visit a cemetery near the Old City of Damascus.

There has been no claim of responsibility. The Hezbollah-run al-Manar TV station said it was carried out by two suicide bombers.

A roadside bomb detonated as a bus passed by and a suicide bomber blew himself up in the Bab al Saghir area, which houses several mausoleums that draw pilgrims from around the world, the Syrian Observa­tory for Human Rights said.

A witness told AFP that the second bomb exploded as passers-by gathered at the scene of the first attack, and state television said a booby-trapped motorcycle was defused nearby.

Syrian state television said at least 120 people were wounded after “terrorists detonated two bombs”.

It broadcast footage of several white buses with their windows shattered, some charred and peppered with shrapnel. Shoes, glasses and wheelchairs lay scattered on ground covered in blood.

Syrian Interior Minister Mohammad Shaar said the attack targeted "pilgrims of various Arab nationalities".

"The sole aim was to kill," he said.

There have been periodic bombings in Damascus, but the stronghold of the regime of President Bashar al Assad has been largely spared the destruction faced by other major cities in six years of civil war.

Shia shrines are a frequent target of attack for extremists of Al Qaeda and the militant Islamic State group (IS), not only in Syria but also in neighbouring Iraq.

The foreign ministry in Damascus condemned "the cowardly terrorist attack which comes in response to victories of the Syrian Arab Army" against militants.

The Sayyida Zeinab mausoleum to the south of Damascus, Syria’s most visited Shia pilgrimage site, has been hit by several deadly bombings during the war.

Twin suicide bombings in the high-security Kafr Sousa district of the capital in January killed 10 people, eight of them soldiers.

That attack was claimed by former Al Qaeda affiliate Fateh al Sham Front, which said that it had targeted Russian military advisers working with the Syrian army.

Peace talks

It was widely seen as an attempt to disrupt UN-broke­red peace talks that took place the following month and which to Fateh al Sham’s anger were supported by its former rebel ally Ahrar al Sham.

United Nations envoy Staffan de Mistura has called a new round of talks for March 23.

Fateh al Sham has been repeatedly bombed in its northwestern stronghold this year, not only by the Syrian army and Russian forces but also by a US-led coalition battling the IS in both Syria and Iraq.

The rift over the UN-brokered talks between the rebels and the government has also seen deadly clashes between militants and their former rebel allies.

The two groups had together seized virtually all of the province of Idlib but are now vying for territorial control.

In Baghdad, the foreign ministry blamed the Damas­cus attack on “takfiri groups”.

In northern Syria, Raqa, the de facto IS capital, is under threat from advancing Turkish-backed Syrian rebels, a US-backed alliance of Kurdish and Arab forces as well as Syrian troops supported by Russia.

Three hundred families of foreign IS fighters fled the city in 24 hours on boats across the Euphrates river to the south, the observatory said.

President Assad said in an interview broadcast on Saturday that recapturing Raqa was a “priority” for his forces.