What Happened

Four gunmen opened fire on a military parade and celebration in Ahvaz, capital of Iran's Khuzestan province, on Sept. 22. The attack killed at least 25 people — including 12 members of Iran's Islamic Revolutionary Guard Corps — and injured more than 70 others. Though it is still unclear who committed the attack, Iranian officials were quick to point the finger at local separatist groups and at international rivals such as the United States and Saudi Arabia.

Why It Matters

The Islamic State claimed responsibility for the shooting through its news agency, Amaq, and published a video that it said showed the assailants. But the video made no mention of the target, and the men in it did not profess allegiance to the Islamic State or to the group's leader, Abu Bakr al-Baghdadi. By contrast, similar videos released to back up previous attack claims have provided more substantial documentation. A video the Islamic State circulated to take responsibility for a 2017 strike on Tehran, for example, included footage taken during the attack.

Iranian media put the blame on regional insurgent groups. Khuzestan, a restive region, is home to a sizable ethnic Arab minority and several Arab separatist groups, including the Patriotic Arab Democratic Movement in Ahvaz and the Arab Struggle Movement for the Liberation of Ahvaz (ASMLA). Both denied involvement in the shooting, but it resembles the kinds of attacks that insurgent outfits have periodically conducted over the past decade in the region, typically targeting businesses, oil infrastructure or security officials. A spokesperson for the ASMLA alleged that a splinter group formed in 2015 was behind the attack. If that claim is true, the shooting was one of the deadliest separatist attacks in Khuzestan.

For the Iranian government, that possibility is cause for concern, not least of all because rivals such as the United States, the United Arab Emirates and Saudi Arabia could try to use the groups against Tehran. In an op-ed last year, John Bolton, who took over as U.S. national security adviser in April, urged the United States to support Khuzestan's Arab population as part of its strategy to counter Iran. And Saudi Crown Prince Mohammed bin Salman ruffled some feathers last May when he said Riyadh would take the fight inside Iran. Attacks on Khuzestan have been sporadic for the past several years, and no clear evidence of foreign involvement in the latest incident has surfaced. But if attacks in the region become more frequent or severe, they could signal a larger problem for Iran.