DAMASCUS, Jan. 31 -- The Islamic State (IS) has claimed responsibility for three deadly bombings that rocked a Shiite district south of the capital Damascus on Sunday, killing over 76 people.

The triple bombings rocked the sprawling Sayyidah Zaynab district, which is 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 explosive belt in a crowed of people, who gathered at the blast site.

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

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

The IS militant group holds deep grudges against the Shiite people, which are considered in the IS methodology as "infidels."

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

The Sayyidah Zaynab tomb became a center 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 on the Syrian government and their religious background about the Shiite-Sunni conflict.

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