(RFE/RLE, AP, Reuters) — Iranian authorities have arrested a member of the country’s military in connection with last month’s deadly attack on a military parade in the city of Ahvaz, local media report.

Judiciary spokesman Gholamhossein Mohseni Ejehi was quoted as saying on October 14 that 11 other military personnel were summoned over the case. Ejehi also said that a military court is probing the case, without providing further details.

Gunmen dressed in military uniforms opened fire during a September 22 parade in the south-western city of Ahvaz, the capital of Khuzestan Province, marking the start of the 1980-88 Iran-Iraq war. The attack left 24 people dead, including civilians and members of the Islamic Revolutionary Guards Corps (IRGC), and dozens of others wounded. Officials said all the attackers died.

Both the extremist group Islamic State (IS) and an Iranian ethnic Arab separatist umbrella group called the Ahvaz National Resistance have claimed responsibility for the assault. Neither group provided conclusive evidence to back up their claim.

Late last month, the semi-official ISNA news agency quoted the head of Iran’s parliamentary committee on national security and foreign policy, Heshmatollah Falahatpisheh, as criticizing security forces for what he described as their negligence during the attack.

Separately, Iranian Intelligence Minister Mahmud Alavi said on October 14 that his ministry had helped to uncover and destroy “300 teams” of militants, the official IRNA news agency reported. Alavi did not give details on the identities of the militants, nor did he indicate when the cells were uncovered.

On October 1, the IRGC said it had fired missiles at militants in Syria to punish the alleged ringleaders of the attack in Ahvaz. “A number of leaders and effective elements” behind the attack were “killed and injured” in the missile strikes in eastern Syria, it said.