A prominent Iranian lawmaker said an attack on a military parade in the southwestern city of Ahvaz that killed 24 people was the result of negligence by security forces, semi-official ISNA news agency reported on Saturday.

The report quoted the head of Iran's parliamentary committee on national security and foreign policy, Heshmatollah Falahatpisheh, as saying a video shot by the intelligence ministry and the army makes this clear.

"The cameraman begged a sniper to shoot the attackers, but the sniper waited for his commander's order," he said, describing the video.

About 92 lawmakers and the intelligence and interior ministers reviewed the video of last Saturday's attack.

"There were eight or nine snipers who were easily able to kill the terrorists in 30 seconds," Falahatpisheh said.

He said one sniper did not at first believe an attack was taking place, but when he saw people were being killed he still did not shoot, saying he didn't get an order to fire.

Falahatpisheh said some of the wounded in the attack had experience fighting the militant Islamic State group in Syria and if they had been armed, they could have prevented the tragedy.

Militants disguised as soldiers opened fire on an annual Iranian military parade in the country's oil-rich southwest, killing 24 people and wounding over 60 in the deadliest terror attack to strike the country in nearly a decade.