Iran's Supreme Leader Ayatollah Ali Khamenei is dead after the United States and Israel launched long-awaited strikes on Iran early Saturday morning, President Trump announced.

U.S. officials believe five to ten other top Iranian leaders who were meeting at a compound in Tehran Saturday are also dead, according to reports.

“Khamenei, one of the most evil people in History, is dead,” Trump wrote in a Truth Social post. “This is not only Justice for the people of Iran, but for all Great Americans, and those people from many Countries throughout the World, that have been killed or mutilated by Khamenei and his gang of bloodthirsty THUGS.”

“He was unable to avoid our Intelligence and Highly Sophisticated Tracking Systems and, working closely with Israel, there was not a thing he, or the other leaders that have been killed along with him, could do. This is the single greatest chance for the Iranian people to take back their Country,” he added.

Earlier on Saturday, Trump vowed to destroy Iran's missile capabilities, "annihilate" their navy, and ensure the nation never obtains a nuclear weapon.

On Saturday morning, Iranian Foreign Minister Abbas Araghchi had told NBC Ayatollah Ali Khamenei and President Masoud Pezeshkian are alive "as far as I know."

"Almost all officials are safe and sound and alive," Araghchi told NBC from Tehran. "We may have lost one or two commanders but that is not a big problem."

Satellite imagery "showed a plume of smoke and extensive damage" at Khamenei's compound, the New York Times reported.

Trump, in a video message released overnight that made clear the goal is regime change, urged the Iranian people to "take over your government" when the operation is finished.

"The hour of your freedom is at hand," Trump said. "This will be, probably, your only chance for generations. . . . This is the moment for action. Do not let it pass."

Trump, asked by NBC News who will lead Iran going forward, said: "I don't know, but at some point they'll be calling me to ask who I'd like," adding that he was "only being a little sarcastic when I say that."

"But look, it's going very well. It's been, you know, we're, we're probably in terms of zero to 10. We're close to the 10 spot, if not there, and it's thus far been going well, but we have a ways to go. Tremendous damage has been inflicted. The leadership is gone," he said. "Large, large portions of the leadership."

America and Israel reportedly plan to carry out several days of attacks, and Trump cautioned that while the administration is taking every step to minimize risks to American personnel, "we may have casualties."

He added, "We're doing this for the future, and it is a noble mission." He urged Iranian security forces to lay down their weapons in exchange for immunity, or face "certain death."

The IDF said more than 200 Israeli Air Force aircraft had struck 500 Iranian targets on Saturday night, in what amounted to the largest aerial attack ever conducted by the Israeli military.

Israel’s military said it had targeted a gathering of senior Iranian officials in the opening strikes, according to the New York Times.

Araghchi said Iran's army "will teach aggressors the lesson they deserve."

The U.S. has been engaged in a weekslong military buildup in the Middle East following vows to help protesters who thronged the streets in January in opposition to the regime, which responded with a deadly crackdown that killed thousands and at least temporarily stifled the unrest.

During his State of the Union address, Trump began to make a broader case for military action against Iran, citing, as he did in his video remarks released overnight, the regime's attacks over the past half-century against U.S. personnel in the region.

Iran immediately launched retaliatory strikes against the U.S. Fifth Fleet headquarters in Bahrain and it remains unclear whether the strike resulted in casualties. Iran also launched waves of ballistic missiles at Israel and targeted the Al Udeid Air Base in Qatar, Ali Al Salem Air Base in Kuwait, Al Dhafra Air Base in the United Arab Emirates.

The United Arab Emirates defense ministry said it intercepted a “new wave” of Iranian missiles on Saturday evening, with fragments from the interceptions falling on areas across Abu Dhabi and Dubai. No injuries were reported.

Lebanon-based Hezbollah urged countries in the Middle East to unite against "perceived aggressions orchestrated by Israel and the United States toward Iran." However, the statement did not mention the possibility of an immediate response.

President Trump spoke with Israeli Prime Minister Benjamin Netanyahu by phone as the strikes were carried out, White House press secretary Karoline Leavitt said. The president "monitored the situation overnight" with his national security team at Mar-a-Lago, she added. Trump and his team "will continue to closely monitor the situation throughout the day."

Meanwhile, in the U.S., several cities stepped up security in response to the strikes on Iran, including New York City and Washington, D.C.

The NYPD said it would be "enhancing patrols to sensitive locations throughout the city, including diplomatic, cultural, religious and other relevant sites." The department said the move was being undertaken as part of "our protocol and out of an abundance of caution."

D.C. police are also "actively coordinating with our local, state, and federal law enforcement partners to safeguard residents, visitors, and businesses," though police said there are “no known threats to DC.”