Militants disguised as soldiers opened fire Saturday on an annual Iranian military parade in the country's oil-rich southwest, killing at least 25 people and wounding over 60 in the deadliest terror attack to strike the country in almost a decade.
Zarif did not specify which regional government he held responsible for the shooting, but Iran's elite Revolutionary Guards said the attackers were funded by Sunni arch rival Saudi Arabia.
He was referencing the moment when at least 24 people including women and children were gunned down at a military parade in southwestern Iran on Saturday.
Mobile phone footage published by the state-run Islamic Republic News Agency showed members of Iran's IRGC and army forces in dress uniform scrambling to the ground while gunfire erupted around them. The Islamic State released a statement that claimed responsibility for Saturday's attack shortly after it occurred, though a separatist Arab militant group also claimed it was behind the attack.
Iran's president today accused an unnamed USA -allied country in the Persian Gulf of being behind a terror attack on a military parade that killed 25 people and wounded 60, further raising regional tensions.
"Iran will respond swiftly and decisively in defense of Iranian lives", he wrote on Twitter.
An unnamed spokesman for the Revolutionary Guards blamed Arab nationalists, who he said were backed by Saudi Arabia, ISNA reported.
The attack took place in the capital of the Khuzestan province, which borders Iraq and is home to a large Sunni population and some of the country's largest oil fields.
"We stand with the Iranian people against the scourge of radical Islamic terrorism and express our sympathy to them at this awful time", Nauert said.
He also said Iran had warned the United Arab Emirates over "offensive remarks" attributed to a UAE "political advisor" following the attack. "They are looking to cut off and separate Iran's energy-rich province of Khuzestan from Iran, which is exactly what Saddam Hussein wanted to do", said Koshcheshm.
The attack struck on Ahvaz's Quds, or Jerusalem, Boulevard.
IS has carried out a major attack in Iran before.
"All four terrorists were quickly neutralised by security forces", Shekarchi told state television.
He added that so far, 15 people, including a child, have been martyred in the terrorist attack.
Iran's Deputy Foreign Minister Abbas Araghchi later said the UAE ambassador would be summoned over "partial statements" in support of the group behind the attack, without elaborating.
A number of Iranian officials, including Zarif and President Hassan Rouhani, are expected to travel to Trump's hometown of New York City next week for high-level meetings at the United Nations General Assembly.
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".
The assailants had hidden weapons near the parade route several days in advance, said Brigadier General Abolfazl Shekarchi, a senior spokesman for Iran's armed forces.
The United States reimposed crippling sanctions on Iran last month, and a new round of even harsher sanctions targeting Iran's vital oil sector is set to go back into effect on 5 November.
The incident comes as the Iranian government tries to parry what it sees as a USA -led war on its economy after President Donald Trump withdrew from the nuclear deal and reimposed sanctions. To bolster his claim, he gave details about one of the attackers that the AP could not immediately verify.
Saturday's attack comes after a coordinated June 7, 2017 Isis assault on parliament and the shrine of Ayatollah Ruhollah Khomeini in Tehran.
This photo shows the aftermath of a terrorist attack on a military parade in the southwestern Iranian city of Ahvaz on September 22, 2018.