ERBIL, Kurdistan Region of Iraq - Iranian officials on Sunday warned that the United States and Israel would be held accountable for the death of Supreme Leader Ayatollah Ali Khamanei, with US President Donald Trump warning Tehran against further retaliatory action.

Khamenei, Iran’s long-ruling Supreme Leader, was killed in an American-Israeli strike on his compound in Tehran on Saturday.

Ali Larijani, secretary of Iran's Supreme National Security Council (SNSC) on Sunday said that Khamenei's killing “burned the heart of the Iranian nation,” warning the US and Israel that “we will burn their hearts.”

“The nation will pass this difficult path with pride,” he added.

Larijani also announced that a three-member council will be formed to temporarily assume leadership duties.

The council will reportedly consist of the president, the judiciary chief, and a jurist from the Guardian Council.

Iran’s Parliament Speaker Mohammad Bagher Ghalibaf said Tehran has prepared for a time like this, “even for the time after the martyrdom of dear Imam Khamenei,” adding that after establishing a leadership council, an “unimaginable power” will form among officials and that the US and Israel will be held accountable.

“Right here, very clearly and openly, I tell [US President Donald] Trump, [Israeli Prime Minister Benjamin] Netanyahu, and their agents and followers—I emphasize again to these two filthy criminals and all their agents—you have stepped on our red line and must pay the price. For us, this is not just an existential war but a suppressed rage whose time for final revenge has come,” Ghalibaf said.

Earlier on Sunday, Trump warned Tehran against conducting “very heavy” retaliatory attacks in the wake of Khamenei’s death, saying if they follow through, the US “will hit them with a force that has never been seen before!”

The US and Israel on Saturday morning launched a large-scale military offensive across Iran, following months of escalating tensions between the two sides. The attacks targeted many of Iran’s political and military leaders, including Khamenei’s residence.

Larijani seems to be one of the few top security officials still alive, while Iranian President Masoud Pezeshkian has yet to make a public appearance or statement.

Khamenei, 86, from Mashhad, was Iran’s highest political and religious authority for nearly 37 years, marking the longest-serving leader since the Islamic Revolution.

He was a leading opponent of the US and Israel, advancing the Islamic Republic’s ideology by supporting regional proxies against both countries, and calling for their elimination.

Iran has declared 40 days of mourning for the late leader.