Terrorists fired on a military parade in Iran’s southwestern city of Ahvaz on Saturday, killing 25 people and wounding more than 60 others, in the bloodiest assault to strike the country in recent years.
The attack, which wounded more than 60 people, targeted a stand where Iranian officials had gathered in Ahvaz to watch an annual event marking the start of the Iraq’s 1980-88 war with Iran.
In a message, Iran’s Leader Ayatollah Seyyed Ali Khamenei slammed the attack, saying the “bitter and regrettable incident… once again revealed the cruelty and wickedness of the Iranian nation’s enemies”.
The Leader blamed the “crime” on “the puppet regimes backed by the US in the region”. He said the terrorists sought to “create insecurity in Iran” but noted that the Islamic Republic will “overcome all hostilities”.
President Hassan Rouhani ordered security forces to identify those responsible for the violence.
The al-Ahvaziya terror group, which seeks separation in Iran’s Khuzestan Province, claimed responsibility for the attack.
Foreign Minister Mohammad Javad Zarif said he held a US ally in the region responsible.
"Terrorists recruited, trained, armed & paid by a foreign regime have attacked Ahvaz," Zarif said in a tweet, adding: "Iran holds regional terror sponsors and their US masters accountable for such attacks".
Zarif did not specify which regional government he held responsible for the shooting, but the Islamic Revolution Guards Corps (IRGC) said the attackers were funded by Saudi Arabia.
"Those who opened fire on civilians and the armed forces have links to the Ahvazi movement," IRGC spokesman Ramezan Sharif told ISNA news agency.
"They are funded by Saudi Arabia and attempted to cast a shadow over the Iranian Armed Forces."
Zarif vowed Iran would "respond swiftly and decisively in defense of Iranian lives".
Brigadier General Abolfazl Shekarchi, a senior spokesman for Iran's Armed Forces, said the attackers had hidden weapons in an area near the parade route several days in advance.
"All four terrorists were quickly neutralized by security forces," Shekarchi told national television.
"Of the four terrorists, three were sent to hell at the scene, while the fourth who had been wounded and arrested went to hell moments ago due to his severe wounds," he said.
He said a four-year-old girl and a wheelchair-bound war veteran were among the dead.
Khuzestan Deputy Governor Ali-Hossein Hosseinzadeh told ISNA that a journalist was also among the dead. He also said earlier that "eight to nine" troops had been killed.
Attacks on the military are rare in Iran. A video distributed to Iranian media showed a soldier picking up a gun and scrambled to his feet as women and children fled for their lives.
“Oh God! Go go go! Lie down! Lie down!” one man screamed as a woman fled with her baby.
“We suddenly realized that some armed people wearing fake military outfits started attacking the comrades from behind (the stage) and then opened fire on women and children,” an unnamed wounded soldier told national TV. “They were just aimlessly shooting around and did not have a specific target.”
The gunmen were trained by two Persian Gulf Arab states and had ties to the United States and Israel, according to Shekarchi.
"They are not from Daesh or other groups fighting (Iran's) Islamic system ... but they are linked to US and (Israel's intelligence agency) Mossad," he told IRNA.
On June 7, 2017, 17 people were killed and dozens wounded in simultaneous attacks in Tehran Parliament and the mausoleum of Ayatollah Rouhollah Khomeini, the founder of the Islamic Republic – the first deadly assault claimed by the Daesh terror group inside Iran.
In a message of condolence, Russian President Vladimir Putin said he was "appalled by this bloody crime."
"This event once again reminds us about the necessity of an uncompromising battle against terrorism in all of its manifestations."
Other countries including Iraq, Pakistan and Britain condemned the terrorist attack and offered condolences to the Iranian nation.
Press TV, Reuters, AFP and AP contributed to this story.