Iran's intelligence ministry said Tuesday that investigators had found last week's deadly attack on a military parade in the mainly ethnic-Arab southwestern city of Ahvaz was mounted by "jihadist separatists".
"The five members of a terrorist squad affiliated to jihadist separatist groups supported by Arab reactionary countries were identified," the ministry said in a statement posted on its website.
"The terrorists' hideout was found and 22 people involved (in the attack) were arrested," it said, adding that explosives were seized along with military and communications equipment.
"Foreign sponsors and supporters of this terrorist act have also been identified. More information will be provided on them in due course," the statement said.
Twenty-four people were killed when gunmen attacked the Saturday parade in Khuzestan province commemorating the start of the 1980-1988 Iran-Iraq war.
Iranian officials were quick to point the finger at Arab separatists, backed by Gulf Arab allies of the United States.
They said that the four gunmen had been killed. Khuzestan, which has a large ethnic Arab community, was a major battleground of the 1980s war with Iraq and it saw unrest in 2005 and 2011.
A movement called the "Ahvaz National Resistance" and the Islamic State jihadist group both claimed responsibility.