The US ambassador to the United Nations has dismissed Iran's assertion that Washington and its Gulf allies are to blame for a deadly attack at a military parade and says Tehran should look closer to home.

Before leaving for the United Nations on Sunday, Iranian President Hassan Rouhani accused other countries, including the US, of provoking the attack killed 25 people and wounded 60 on Saturday.

At least 12 of the dead served in the Revolutionary Guard, an elite paramilitary unit - and among the other victims was a four-year-old boy.

An Iranian army member carries away a child from a shooting scene during a military parade marking the 38th anniversary of Iraq's 1980 invasion of Iran, in the southwestern city of Ahvaz, Iran. (AP) (AP)

Iranian soldiers, women, and children lay down and run during a terror attack that occurred at military parade in the city of Ahvaz, southern Iran. (AAP) (AP)

The attack, in which militants disguised as soldiers opened fire on an annual Iranian military parade in Ahvaz, was the deadliest attack in the country in nearly a decade. (AAP) (AP)

But US ambassador Nikki Haley dismissed his comments as rhetoric.

"He's got the Iranian people protesting, every ounce of money that goes into Iran goes into his military, he has oppressed his people for a long time and he needs to look at his own base to figure out where that's coming from," she told CNN's State of the Union.

"He can blame us all he wants. The thing he's got to do is look at the mirror."

Iran's Revolutionary Guards vowed to wreak "deadly and unforgettable" vengeance for the attack.

Civilians try to take shelter in a shooting scene, during a military parade marking the 38th anniversary of Iraq's 1980 invasion of Iran, in the southwestern city of Ahvaz, Iran. (AP) (AP)

Tensions have been on the rise in Iran since the Trump administration pulled out of the 2015 nuclear accord with Iran in May and began restoring sanctions that were eased under the deal. (AAP) (AP)

There has been a blizzard of furious statements from top Iranian officials blaming the US and Gulf kingdoms for the bloodshed and threatening a tough response.

"America wants to cause chaos and unrest in our country so that it can return to this country, but these are unreal fantasies and they will never achieve their goals," Rouhani said.

Haley was asked about comments made Saturday night after the attack by President Donald Trump's personal lawyer, Rudy Giuliani. He told an Iranian opposition group that US sanctions on Iran are leading to economic pain that could lead to a "successful revolution".

Giuliani has made similar comments before on Iran, and the State Department has said he does not speak for the administration.

Iranian soldiers, women, and children lay down and run during a terror attack that occurred at military parade in the city of Ahvaz, southern Iran. (AAP) (AP)

Wounded military personnel are carried into an ambulance after a shooting during a military parade marking the 38th anniversary of Iraq's 1980 invasion of Iran, in the southwestern city of Ahvaz, Iran. (AP) (AP)

The UN ambassador, without mentioning Giuliani, told CNN, "The United States is not looking to do regime change in Iran."

Trump administration policy does not seek a change of government even though it is reimposing sanctions that are crippling Iran's economy after Trump pulled out of the 2015 Iran nuclear agreement.

Haley said Washington was trying to counter Iranian malign activities in the region as Tehran continued to test ballistic missiles, support terrorism and sell arms.

Iran's Revolutionary Guards have vowed to wreak "deadly and unforgettable" vengeance for the attack. (AAP) (AP)

Iran's president has accused an unnamed US-allied country in the Persian Gulf of being behind a terror attack on a military parade that killed 25 people and wounded 60. (AAP) (AP)

Saturday's attack, in which militants disguised as soldiers opened fire on an annual Iranian military parade in Ahvaz, was the deadliest attack in the country in nearly a decade. Women and children scattered along with once-marching Revolutionary Guard soldiers as heavy gunfire rang out, the chaos captured live on state television.

The region's Arab separatists, once only known for nighttime attacks on unguarded oil pipelines, claimed responsibility for the assault, and Iranian officials appeared to believe the claim. The separatists accuse Iran's Persian-dominated government of discriminating against its ethnic Arab minority. Khuzestan province also has seen recent protests over Iran's nationwide drought, as well as economic protests.

Tensions between the US and Iran have been especially tense since the Trump administration pulled out of the 2015 nuclear accord with Iran in May and began restoring sanctions that were eased under the deal. It also has steadily ramped up pressure on Iran to try to get it to stop what Washington calls its "malign activities" in the region.

Iran has summoned diplomats from Britain, Denmark and the Netherlands for allegedly harboring "members of the terrorist group" that launched the attack. (AAP) (AP)

The US government nevertheless strongly condemned Saturday's attack and expressed its sympathy, saying it "condemns all acts of terrorism and the loss of any innocent lives."