The Islamic State claimed responsibility on Thursday for two explosions that killed nearly 100 people and wounded scores at a ceremony in Iran to commemorate commander Qassem Soleimani, who was killed by a U.S. drone in 2020.
The group posted a statement on its affiliate Telegram channels.
Multiple officials in the Iranian regime had blamed Israel for the terror attack.
"The non-suicidal nature of the terrorist attack in Kerman shows that it is an act of the Zionist regime," said Mojtaba Zolnouri, the Iranian parliament's deputy speaker. "We will punish the Zionist regime with a revenge that will have global operational value."
Mohammad Jamshidi, deputy chief of staff to Iran's president, said that both Israel and the United States bore responsibility.
"Washington says USA and Israel had no role in terrorist attack in Kerman, Iran," Jamshidi wrote on X, formerly Twitter. "Really? A fox smells its own lair first. Make no mistake. The responsibility for this crime lies with the US and Zionist regimes and terrorism is just a tool."
The United States denied on Wednesday any involvement in the explosions and said it also had no reason to believe Israel was involved. It said the blasts appeared to represent "a terrorist attack" of the type carried out in the past by Islamic State.
Tehran often accuses its archenemies, Israel and the United States, of backing anti-Iran militant groups that have carried out attacks against the Islamic Republic in the past. Baluchi militants and ethnic Arab separatists have also staged attacks in Iran.
The U.S. assassination of Soleimani in a Jan. 3, 2020, drone attack at Baghdad airport and Tehran's retaliation—by attacking two Iraqi military bases that house U.S. troops—brought the United States and Iran close to full-blown conflict.
As chief commander of the elite Quds force, the overseas arm of Iran's Revolutionary Guard Corps, Soleimani ran clandestine operations abroad and was a key figure in Iran's longstanding campaign to drive U.S. forces from the Middle East.
Tensions between Iran and Israel, along with its ally the United States, have reached a new high over Israel's war on Iran-backed Hamas militants in Gaza in retaliation for their Oct. 7 rampage through southern Israel.
Yemen's Iran-backed Houthi militia have attacked ships they say have links to Israel in the entrance to the Red Sea, one of the world's busiest shipping lanes.
U.S. forces have come under attack from Iran-backed militants in Iraq and Syria over Washington's backing of Israel and have carried out their own retaliatory air strikes.