Unidentified gunmen opened fire on a military parade in Iran’s southwestern city of Ahvaz on Saturday, killing at least 24 people including civilians and wounding dozens of others, the official Islamic Republic News Agency (IRNA) said.

“The number of martyrs of the terrorist incident on Saturday morning in Ahwaz has reached 24. The toll is likely to rise due to many wounded in critical condition,” IRNA reported quoting an unnamed source.

Civilians, including women and children, were among those killed, while at least 53 people have been transferred to local hospitals, according to the source.

Most of the martyrs were from the Guards, said Ali Hossein Hossein Zadeh, deputy to the Khuzestan provincial governor, referring to the Islamic Revolution Guards Corps, or IRGC.

The attackers disguised themselves as members of the Iranian armed forces and opened fire, according to IRNA, targeting officials in attendance. Those dignitaries were not harmed in the attack, it said.

The first bursts of gunfire can be heard in state TV footage posted to Twitter. At first, the military procession continues, but seconds later, another burst is heard, sending the column of soldiers and spectators running.

Two of the gunmen are under arrest, while two others were shot dead, IRNA reported.

No group has yet claimed responsibility for the attack, but a spokesman for the Revolutionary Guards pointed the finger at ethnic Arab separatists.

General Ramadan Sharif told the semi-official Iranian Students’ News Agency the attackers were from the separatist Ahvaz Movement, which seeks to establish an independent Arab state in Khuzestan province, where the attack took place.

He blamed Saudi Arabia for fueling the movement.

Iranian Foreign Minister Mohammad Javad Zarif also appeared to blame rival Riyadh for the attack.

“Terrorists recruited, trained, armed & paid by a foreign regime have attacked Ahvaz. Children and journos among casualties. Iran holds regional terror sponsors and their US masters accountable for such attacks. Iran will respond swiftly and decisively in defense of Iranian lives,” he tweeted.

Iran has intervened in the wars in Syria and Iraq and plays an influential role in Yemen, but this was a rare attack on its own soil.

A 2017 double bombing in Tehran claimed by the Sunni extremist group Islamic State left 18 people dead.