The Islamic State has claimed responsibility for the attack, continuing its attempt to inflame the tensions between Iraq’s Shiites and Sunnis. According to a statement by the terror group, the attack had been carried out by three men wearing suicide belts.

According to reports, one man detonated an explosive belt at the external gate of the mausoleum around 11 p.m. local time near where police were on guard. Another man then stormed the site and began to shoot at worshippers before he blew himself up in the middle of the crowd. Anther man was gunned down by security before he could detonate his explosive belt. The use of grenades was also reported.

The attack comes just days after a truck bomb in a Shiite district in Baghdad killed nearly 300 people in what was the deadliest attack in the country’s capital in years.