Iranian boys hold images of one of the victims, 4-year-old Mohammad Taha Eghdami, during a public funeral ceremony for those killed in the attack in the southwestern Iranian city of Ahvaz on September 24.
Of the 25 people killed, 12 were from Ahvaz and the rest from elsewhere in Khuzestan.
Fars and IRNA news agencies said on Monday five attackers were killed, not four as previously reported by state media.
Ethnic Arab separatists and the Islamic State group (IS) have issued competing claims that they carried out the attack, which was the deadliest in Iran in nearly a decade.
Ayatollah Ali Khamenei, Iran's supreme leader, said on Monday that the attack was carried out by terrorists paid by Saudi Arabia and the UAE, Iran's regional rivals.
Blaming the triangle of the U.S., the Zionist regime of Israel and Saudi Arabia for the horrific crime against the Iranian people, the general said the people of Khuzestan who have resisted eight years of war in the 1980s would not be shocked by "four mosquitos" that carried out the Saturday attack.
Iran's elite Revolutionary Guards vowed to exact "deadly and unforgettable" vengeance for the attack with Tehran still accusing Gulf Arab states of backing the gunmen.
In his address, IRGC deputy head Hossein Salami reiterated accusations against the United States and Israel and warned the two countries to expect a "crushing and devastating" response from Tehran.
The victims were primarily members of the Iranian Revolutionary Guard.
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"We stand with the Iranian people against the scourge of radical Islamic terrorism and express our sympathy to them at this bad time".
At Monday's funeral, however, those attending rallied around the Iranian government and its soldiers.
Rouhani's remarks could refer to Saudi Arabia, the United Arab Emirates or Bahrain - close USA military allies that view Iran as a regional menace over its support for militant groups across the Middle East.
General Hossein Salami, acting commander of the Revolutionary Guard vowed revenge on the perpetrators of the attack and what he called the "triangle" - or Saudi Arabia, Israel and the United States - saying operatives would be harshly punished.
The UAE minister of state for foreign affairs, Anwar Gargash, for his part, stressed his country's rejection of acts of terrorism and accused Tehran of a campaign of "official incitement" against the Emirates.
A spokesman for the al-Ahwaz National Resistance, an umbrella movement for Arab separatist groups fighting for independence for Khuzestan province, has said it carried out the attack.
Iran has said it has arrested a large network of suspects over Saturday's attack. "It is Americans who instigate them and provide them with necessary means to commit these crimes", Rouhani said before leaving for the U.N. General Assembly in NY.
It answers to Ayatollah Khamenei and has an estimated 125,000-strong military with army, navy and air units.
Shi'ite Iran is at odds with Western-allied Sunni Muslim Saudi Arabia for predominance in the Middle East.