Iran live updates: 7th killed service member is identified

The U.S. Embassy in Muscat, Oman, on Sunday issued a shelter-in-place order for all Americans in the country due to "ongoing activity outside of Muscat."

The northern coast of Oman, on which Muscat is located, faces the southeastern coast of Iran across the Gulf of Oman. The country has traditionally played a mediating role between Iran and the U.S.

As of Sunday morning, Oman was the only Gulf nation not to have been attacked by Iran.

Ayatollah Ali Khamenei was killed during the "opening blow" of the U.S.-Israel operation on Saturday, Israeli Defense Minister Israel Katz said in a post on X on Sunday.

Katz congratulated Israeli Prime Minister Benjamin Netanyahu for his "leadership and determination," and the Israel Defense Forces for its "brilliant execution."

-ABC News' Jordana Miller and Ellie Kaufman

Iranian state media confirmed the deaths of Rear Adm. Ali Shamkhani, the secretary of the Defense Council, and Maj. Gen. Mohammad Pakpour, the commander-in-chief of the Islamic Revolutionary Guards Corps, in strikes on Saturday.

ABC News' Somayeh Malekian and Ellie Kaufman

In a new post on his social media platform on Sunday morning, President Donald Trump warned Iran not to escalate its attacks, following U.S. strikes against the country.

"Iran just stated that they are going to hit very hard today, harder than they have ever hit before," Trump wrote in the post. "THEY BETTER NOT DO THAT, HOWEVER, BECAUSE IF THEY DO, WE WILL HIT THEM WITH A FORCE THAT HAS NEVER BEEN SEEN BEFORE!"