Iran’s president on Sunday accused an unnamed U.S.-allied country in the Persian Gulf of being behind a terror attack on a military parade that killed 25 people and wounded 60.

Hassan Rouhani’s comments came as Iran’s Foreign Ministry also summoned Western diplomats over them allegedly providing havens for the Arab separatists who claimed Saturday’s attacks in the southwestern city of Ahvaz.

The attack in Ahvaz, which saw women and children flee with uniformed soldiers bloodied, has further shaken the country. Rouhani’s remarks could refer to Saudi Arabia, the United Arab Emirates or Bahrain — close U.S. military allies that view Iran as a regional menace over its support for militant groups across the Middle East.

“All of those small mercenary countries that we see in this region are backed by America. 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 New York.

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 Guard responded to the attack on Sunday, warning it would seek “deadly and unforgiving revenge in the near future.”

The U.S. government strongly condemned Saturday’s attack and expressed its sympathy, saying it “condemns all acts of terrorism and the loss of any innocent lives.”

Overnight, an impromptu candle-light vigil in Ahvaz honored the dead and wounded. Iran planned a day of mourning Monday and funerals for those killed.

Among them is 4-year-old Mohammad Taha, who was captured by a photographer being carried away from the attack by a Guardsman in full dress uniform and sash. The photograph, showing the boy bloodied and helpless, shocked Iran.

“He was wearing a black shirt when he was martyred,” a doctor said, standing next to the boy’s tiny corpse, now wrapped in a blue body bag.