A gunman, on Wednesday, opened fire on worshippers of a Shia shrine-- Shah Cheragh. At least 20 were killed and dozens of others were wounded.
The radical Sunni Muslim jihadist group Islamic State, via Telegram channels, claimed responsibility for the attack.
The semi-official Tasnim news agency reported that the attackers were in a car as they shot at pilgrims and staff at the entrance to the shrine. Two of the three terrorists have been arrested. The police are on the lookout for the third person.
"This crime will definitely not go unanswered, and the security and law enforcement forces will teach a lesson to those who designed and carried out the attack," Iranian President Ebrahim Raisi said, DW reported.
The governor of Fars province told CNN, “the terrorist first targeted the servant and guard of the shrine and intended to attack the congregational evening prayers, but one of the servants shut the door on him.”
The attack took place on the same day riot police fired at protesters who had come out against the custodial death of 22-year-old Mahsa Amini for failing to adhere to the country's conservative dress code. The riot police also used tear gas at protesters, who had gathered at Amini's home town of Saqqez, a city in the Kurdistan province to mark 40 days following Amini's death.
