"Our time together was a reminder of the work we have in front of us to secure the release of all remaining hostages," said the U.S. president.

School promises to step up security, restrict access to campus after rabbi tells Jewish students to stay home until campus is safe, though Hillel says they should not flee.

"We honor the Rebbe’s birthday every year, but we know this year is different," the U.S. president stated.

"Our enemies look at this government, smell weakness and raise their heads," said Israeli opposition leader Yair Lapid.

Iranian Foreign Minister Hossein Amirabdollahian said on Sunday that Iran gave neighboring countries and Israel's ally the United States 72 hours' notice it would launch the strikes.

According to the FSB's public relations center, the assailant intended to carry out the attack during a period of significant congregation at the religious Jewish institution.