Sgt. Benjamin N. Pennington, 26, was killed in Saudi Arabia.
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 in Tehran on the first day of strikes. His son Mojtaba Khamenei was chosen on Sunday to succeed him.
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.
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In a brief phone call with a reporter from The Washington Post just after 4 a.m. on Saturday, President Donald Trump told the paper that all he wants is "freedom for the people" of Iran.
"All I want is freedom for the people," Trump said when asked about what he hoped his legacy would be as a result of the U.S. operation. "I want a safe nation, and that's what we're going to have."
Defense Secretary Pete Hegseth and Gen. Dan Caine, the chairman of the Joint Chiefs of Staff, are at Mar-A-Lago with President Trump monitoring today's strikes, according to a source familiar.
-ABC News' Luis Martinez
The IDF says it has identified another wave of "missiles launched from Iran toward the territory of the State of Israel. "
Sirens sounded in central Israel.
The United Arab Emirates' ministry of defense said a civilian was killed as a result of fallen debris after "a blatant attack involving Iranian ballistic missiles."
The statement from the ministry said "air defence systems dealt with the missiles with high efficiency and successfully intercepted a number of missiles."
In Israel, the national emergency service said at least one person suffered blast injuries on Saturday.
The man, who injured in northern Israel, was in "mild condition," according to the service.
The emergency service said its teams also treated "several individuals who were injured on their way to protected spaces, all fully conscious, as well as to people suffering from anxiety across the country."
Iran's state broadcaster IRIB reported that five girls were killed when Israeli strikes targeted an elementary school in the southern city of Minab on Saturday.
There was no immediate comment from the Israeli military.
