An activist-run monitoring group says a car bomb has exploded in a suburb of Damascus that his home to one of the holiest Shiite shrines in Syria, killing six people.

Syrian state TV confirmed the car bomb attack in the government-held Sayyida Zeinab district, but did not provide details on casualties.

Shiite fighters from Lebanon, Iraq and Iran who have flocked to Syria to fight alongside President Bashar Assad's forces often say they are there to defend the Sayyida Zeinab shrine. The shrine is heavily guarded.

A previous blast in the suburb, claimed by the Islamic State group, killed some 130 people in February.