Last year’s attack, for which two people convicted of being linked with ISIL were executed, left 13 dead and 40 injured.

Details have yet to be confirmed, but officials and state-linked media said two shooters entered the Shah Cheragh shrine through its southern gate on Sunday at around 7pm (15:30 GMT) and opened fire on security staff and worshippers, killing at least one person and wounding several others.

Yadollah Bouali, the provincial commander of the Islamic Revolutionary Guard Corps (IRGC), told state television one shooter was arrested at the scene with an assault rifle and eight magazines full of ammunition. The second gunman fled the scene.

Videos online showed people running in panic outside the shrine and shutting down their shops. Images showed bullet holes in walls and eyeglasses and blood on the ground.

The shrine, located in the province of Fars and one of the most important in Shia Islam, was hit by a similar attack on October 26, 2022.

At the time, a lone gunman entered the shrine with an automatic rifle, shooting a group of pilgrims and staff. Authorities said the gunman killed 13 people and injured 40 others before being killed by security forces.

The ISIL (ISIS) armed group released a video through its Amaq website and took responsibility for the attack.

The group was also responsible for coordinated 2017 attacks on the Iranian parliament and the mausoleum of former Supreme Leader Ayatollah Ruhollah Khomeini in Tehran.

In early June, Iran executed two men said to have been in contact with ISIL operatives in neighbouring Afghanistan who provided the gunman with the rifle and took him to the site of the shooting.

Three more men were also tried and given prison sentences ranging from five to 25 years for working with the armed group.

Last year’s assault on the shrine also came as Iran was rocked by nationwide protests that started in September 2022 following the death in custody of 22-year-old Mahsa Amini, who was arrested for alleged noncompliance with the country’s mandatory dress code for women.

It took place 40 days after Amini’s death, when thousands gathered to mark the occasion in her hometown in northwestern Iran.

Iranian authorities, who blamed “riots” backed by foreign powers for undermining the country’s security, said at the time that the unrest paved the way for the Shah Cheragh attack to take place.