Damascus: The Islamic State terror group on Sunday claimed responsibility for three deadly bombings that rocked a Shiite district south of the capital Damascus earlier in the day killing over 76 people.

The triple bombings rocked the sprawling Sayyidah Zaynab district, which was guarded by the Shiite Lebanese Hezbollah group, in the southern countryside of Damascus.

The first explosion was caused by a booby-trapped car that targeted a passenger bus on the al-Sudan street in that area, state news agency SANA said, adding that after the first bombing, two suicide bombers detonated their explosives-laden belts in the crowed that gathered at the blast site.

Meanwhile, a source familiar with the incident told Xinhua that 76 people were killed in the explosions, adding that the death toll could rise as tens of wounded people were critical.

The Syrian Observatory for Human Rights, an opposition monitor, said 25 Shiite fighters were among those killed.

The IS militant group holds deep grudge against the Shiite people, who are considered as "infidels" by the IS.

The enmity toward the Shiite people also emanates from the terror group's battles against Hezbollah and the Syrian army across Syria.

The Sayyidah Zaynab tomb became a centre of religious studies of the adherents of the Shiite sect of Islam and a destination of mass pilgrimage by Shiite Muslims from across the Muslim world.

On June 14, 2012, a suicide car bomb tore through that district, wounding around 14 people.

Since mid-summer 2012, the district has been under frequent attacks and shelling by the ultra-radical rebels, who aim to attack the Shiite people due to their supportive stance towards the Syrian government and their religious background of the Shiite-Sunni conflict.

As the district holds religious significance for the Shiite people, Hezbollah sent fighters to protect the shrine and manned checkpoints surrounding it.