A double bomb attack targeting Shia Muslim pilgrims in Damascus killed at least 40 Iraqis and wounded 120 more who were going to pray at a nearby shrine, the Iraqi foreign ministry said.

There was no immediate claim of responsibility for Saturday’s attack, which the Hezbollah-run Al-Manar TV station said was carried out by two suicide bombers.

Footage broadcast by Syrian state TV showed two badly damaged buses with their windows blown out. The area was splattered with blood and shoes were scattered on the ground.

Syrian President Bashar al-Assad has received support in the country’s civil war from Shia militias from countries including Iraq, Afghanistan and Lebanon. Iran, which backs Lebanese Hezabollah, is also a key ally.

The attack took place at a bus station where the pilgrims had been brought to visit the nearby Bab al-Saghir cemetery, named after one of the seven gates of the Old City of Damascus.

The second blast went off some 10 minutes after the first at around 10am local time, inflicting casualties on civil defence workers who had gathered to tend to the casualties, according to Al-Manar.

The pilgrims were due to pray at the cemetery after visiting the Sayeda Zeinab shrine just outside Damascus, the channel reported.

Sayeda Zeinab, the granddaughter of the Prophet Mohammad, is venerated by Shias and her shrine is a site of mass pilgrimage for Shias from across the world. It has also been a magnet for Shia militiamen in Syria.

The Syrian Observatory for Human Rights, a UK-based organisation that reports on the war, said the death toll was at least 44 – that figure is set to rise given the number of serious injuries, the organisation added.

In June Isis claimed responsibility for bomb attacks near the Sayeda Zeinab shrine. The last bomb attack in Damascus was in January, when a suicide bomber hit the heavily policed Kafr Sousa neighbourhood, killing at least seven people.