Iranian officials have accused U.S. allies in the region of being behind a deadly attack on a military parade in the southwest of the country that left 29 people dead and dozens wounded amid claims of responsibility by two groups -- an ethnic Arab separatist group and the extremist group Islamic State (IS).
Neither Iranian officials nor the two groups claiming responsibility for the attack presented evidence to back up their claims.
According to domestic media, members of Iran's Islamic Revolutionary Guards Corps (IRGC) were killed, along with civilians watching the parade, including a 4-year-old child.
"Their crime is a continuation of the plots of the regional states that are puppets of the United States, and whose goal is to create insecurity in our dear country," Iranian Supreme Leader Ayatollah Ali Khamenei said in a statement issued on September 22 a few hours after gunmen attacked a parade in the city of Ahvaz, the capital of the southwestern Khuzestan province, where the majority of Iran's ethnic Arabs live.
Khamenei did not specify which states he was referring to.
Relations between regional rivals Iran and Saudi Arabia -- Washington's main Arab ally in the Middle East -- have been deteriorating, with both sides accusing each other of creating instability in the region. Tehran has claimed in the past that Saudi Arabia provides support to separatists among its ethnic Arab minority.
Gallery: Gunmen Attack Military Parade In Southwestern Iran
Scott Lucas, an Iran specialist at Birmingham University in Britain and editor of the EA World View website, tells RFE/RL that Tehran's blaming of regional foes and the United States for domestic unrest is not new, while adding that it is "accentuated now by U.S. withdrawal from the nuclear deal, imminence of comprehensive sanctions, and worsening of the Iranian economy."
Tensions between Tehran and the United States have been escalating following a May decision by U.S. President Donald Trump to withdraw from the 2015 nuclear deal and reimpose tough sanctions on Iran.
"I think Ahvaz --- inevitably, and not at all diminishing the scale of the killing of innocents --- was going to be situated by regime officials within the narrative of a U.S.-Saudi campaign to undermine the Islamic republic," Lucas says.
"The overriding concern right now is the economic crisis and the impact of U.S. sanctions, linked to Iran's regional contest with Riyadh and conflicts such as Syria, Yemen, and Iraq," he adds.
Persian Gulf 'Mercenaries'
On September 23, Iran's Foreign Ministry summoned the charge d'affaires of the United Arab Emirates, a close Saudi ally, over "irresponsible and disdainful" comments made by a government adviser who reportedly said that attacking a military target cannot be considered a terrorist attack.
For his part, President Hassan Rohani accused the United States of enabling the deadly attack through its support for unnamed Persian Gulf states. Speaking on September 23 shortly before leaving Tehran for the UN General Assembly in New York, Rohani said the perpetrators of the attack and their affiliation were "absolutely clear" to Tehran.
"Those who have caused this catastrophe...were [Iraqi dictator Saddam Hussein's] mercenaries as long as he was alive and then changed masters," he said. "One of the countries in the south of the Persian Gulf took care of their financial, weaponry and political needs," Rohani added.
"All these little mercenary countries we see in this region are backed by America. It is the Americans who incite them," he said.
Ali Vaez, the director of the Iran Project at the International Crisis Group (ICG), tells RFE/RL that Tehran appears to have intelligence of renewed activities of separatist groups and their ties to some Persian Gulf countries.
"That there was a deafening silence from Saudi Arabia and its gulf allies in the hours after the assault is for Tehran further evidence of their culpability," Vaez says.
"The fact that senior U.S. officials like John Bolton, before he became national-security adviser, had openly advocated supporting Iran's ethnic and sectarian minorities as means of destabilizing Iran deepens Tehran's suspicions," he adds.
People rush for shelter as shooting starts during a military parade in the southwestern city of Ahvaz on September 22.
An Iranian ethnic Arab opposition group called the Ahvaz National Resistance, which seeks a separate state in Khuzestan province, claimed responsibility for the attack without providing any evidence.
A spokesman for the group, Yagoub Hor Altasteri told the Persian service of German broadcaster Deutsche Welle that the attack was "a legitimate act" in response to what he described as "the transfer of water", "poverty," and "executions."
Ethnic Arabs in the oil-rich province of Khuzestan have long complained of social, cultural, and political discrimination and injustice. The region was the scene of unrest in 2005 and 2011 that resulted in dozens of arrests, rights groups, including Human Rights Watch, have reported.
Some officials and the official government news agency IRNA confirmed the claim by the Ahvaz National Resistance umbrella group, which was created in 2005. It reportedly includes a military wing as well as political entities, including the Arab Struggle Movement for the Liberation of Ahvaz.
"The individuals who fired at the people and the armed forces during the parade are connected to the Al-Ahvazia group, which is fed by Saudi Arabia," IRGC spokesman Ramezan Sharif was quoted as saying by state media.
IS Claim Rejected
A claim of responsibility by the extremist group Islamic State (IS), which also took responsibility for the 2017 twin attacks on the Iranian parliament and the mausoleum of Islamic republic founder Ayatollah Ruhollah Khomeini, was dismissed by a military spokesman.
Abolfazl Shekarchi, a senior spokesman for the Iranian military, said "terrorists" behind the Ahvaz attack were not members of IS or groups opposed to the Islamic establishment.
"They are individuals who entered the country after being trained and organized by two Persian Gulf countries," Shekarchi was quoted as saying by domestic media.
"These individuals affiliated with the United States and Mossad committed [the attack]," he said. In a statement issued on September 23, the powerful IRGC vowed "deadly and unforgettable vengeance in the near future."