NEW YORK, Sept. 23 (CGTN) -- The US ambassador to the UN has urged Iran to "look in the mirror" for the causes of a deadly attack on a military parade that killed 25 people on Saturday.

Nikki Haley said it had happened because Iranian President Hassan Rouhani had "oppressed his people for a long time."

"He needs to look at his own base to figure out where that's coming from. I think the Iranian people have had enough," Haley told CNN.

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

She was responding to Rouhani's fierce criticism of the US, in which he blamed the US and Gulf states of provoking the bloodshed and threatening a tough response.

Four assailants fired on a viewing stand in the southwestern city of Ahvaz where Iranian officials had gathered to watch an annual event marking the start of the Islamic Republic's 1980-88 war with Iraq. Soldiers crawled about as gunfire crackled. Women and children fled for their lives.

The ISIL's Amaq agency posted a video of three men in a vehicle who it said were on their way to carry out the attack.

A man wearing a baseball cap emblazoned with what appears to be a Revolutionary Guard logo discussed the impending attack in Farsi in the video. “We are Muslims, they are kafirs (non-believers),” the man says. He adds: “We will destroy them with a strong and guerrilla-style attack, inshallah (God willing).”

Ahvaz National Resistance, an Iranian ethnic Arab opposition movement which seeks a separate state in oil-rich Khuzestan province, also claimed responsibility for the attack.

Neither of them provided evidence.

Tehran also summoned diplomats from Denmark, the Netherlands and Britain for allegedly hosting members of the group suspected of links to Saturday's attack.

President Rouhani will face US President Donald Trump at the UN General Assembly this week.