He is the son of assassinated Supreme Leader Ayatollah Ali Khamenei.
President Donald Trump announced "major combat operations" against Iran on Feb. 28, with massive joint U.S.-Israel strikes attack targeting military and government sites, officials said.
Iranian state television confirmed that Ayatollah Ali Khamenei was among those killed by airstrikes in Tehran on the first day of strikes. His successor is yet to be named.
Iran is responding to the operation with missile and drone attacks targeting Israel, regional U.S. bases and multiple Gulf nations. Israel is also intensifying its long-running strike campaign against the Iran-backed Hezbollah militia in Lebanon.
(Read previous Iran live updates here.)
Watch special coverage on Nightline, "War with Iran," each night on ABC and streaming on Disney+ and Hulu.
The State Department advised U.S. government personnel not to travel to Azerbaijan's Nakhchivan region in a new security alert issued Thursday.
The alert comes after Azerbaijan's Foreign Ministry said earlier Thursday that drones struck the city of Nakhchivan, just north of the country's border with Iran. One drone hit the city's airport, the ministry said.
House Speaker Mike Johnson continued to argue that the U.S. is not at war with Iran, following the failed war powers resolution vote in the House on Thursday.
"We are not at war. We have no intention of being at war," he told reporters. "The Department of War has made it very clear -- this is a limited operation. It's an operation that is limited in its scope and duration."
Johnson's comments come a day after President Donald Trump said: "I have to go back and look at the war. You know, I have a lot of things happening.”
The House speaker said he is "grateful" that the resolution failed.
"It would have been a very dangerous gambit to take the commander-in-chief's ability away to complete this mission. Would have been a very serious misstep by Congress," Johnson said.
-ABC News' Lauren Peller
President Donald Trump called upon the Iranian Revolutionary Guard, military and police to "lay down their arms" against the U.S. and Israel as the conflict in Iran surges on -- telling these military forces to "take back your country" from the regime.
The president offered these officers immunity, saying they’d face "absolutely guaranteed death" if they declined.
“And I'm once again calling on all members of the Iranian Revolutionary Guard, the military and the police to lay down their arms. They're only going to be killed. And now is the time to stand up for the Iranian people and help take back your country," Trump said during an event on Thursday at the White House.
"You're going to have a chance, after all these years, to take back your country. Accept immunity, we'll give you immunity," he continued.
"So you'll be perfectly safe with total immunity, or you'll face absolutely guaranteed death. And I don't want to see that. They don't want to see it either," he added.
-ABC News' Isabella Murray
Defense Secretary Pete Hegseth pushed back on the notion that the war is expanding in the Middle East due to Iran's attacks on U.S. bases in the Gulf or that there's "chaos."
"Nothing could be further from the truth," he said during Thursday's briefing. "If anything, what Iran is doing by targeting allied countries that would otherwise want to stay out of this, they've actually pulled them into the American orbit."
Hegseth argued it's "actually firming up the unity of the resistance."
"Now you've got UAE and Qatar and Bahrain and Saudi and Kuwait and others saying, 'Hey, we're with you here. We'll shoot with you. We'll fly with you,'" he said.
