Gunmen opened fire on a military parade in Iran on Saturday, killing 24 people including elite Revolutionary Guard troops, in one of the deadliest attacks in the country in recent years.

Four assailants targeted a stand where Iranian officials had gathered to watch an annual event in the southwestern city of Ahvaz marking the start of the Islamic Republic's 1980-88 war with Iraq.

There were reports they were dressed in Islamic Revolutionary Guards Corp (IRGC) uniforms.

A pan-Arab, anti-government group called the Arab Struggle Movement for the Liberation of Ahvaz appeared to take responsibility for the attack, which wounded more than 50 people. Among the dead were eight IRGC servicemen, as well as women and children.

Islamic State also later claimed it, but Iranian authorities deemed it not to be credible.