“Out of an abundance of caution, U.S. government employees and their family members are restricted from personal travel outside the greater Tel Aviv, … Jerusalem, and Be’er Sheva areas until further notice,” reads the U.S. Embassy security alert, issued Thursday.

The attack killed two senior members of the Islamic Revolutionary Guard Corps and five other officers, Iran said.

While Israel has not publicly claimed responsibility, U.S. officials told The Washington Post that Pentagon officials were frustrated that Israel did not notify the United States before the April 1 strike, which they assess increases risks to U.S. forces in the Middle East.

Iran’s supreme leader, Ayatollah Ali Khamenei, said Israel would be “punished” and “regret this crime.” With Israel’s military on high alert last week, Israel has vowed to strike back at Iran “if Iran attacks from its territory.”

The head of U.S. Central Command, Gen. Michael “Erik” Kurilla, visited Israel on Thursday, a Pentagon spokesperson said, as the allies coordinate on preparing for Iran’s promised counterstrike. President Biden has repeated that the U.S. commitment to Israel against threats from Iran and its allies is “ironclad.”

“The U.S. Embassy in Jerusalem reminds U.S. citizens of the continued need for caution and increased personal security awareness as security incidents often take place without warning,” the alert said. “The security environment remains complex and can change quickly depending on the political situation and recent events.”

The April 1 strike near a diplomatic compound — traditionally exempted from hostilities — was seen as an escalation in Israel’s multi-front battles against Iranian-backed groups in the region, which have intensified during its war in Gaza.

The United States has previously issued travel warnings during the war, and a rare “worldwide caution” advisory to all Americans overseas in October, citing “the potential for violence and increased tensions” globally.

Confrontations in Iraq, Lebanon, Syria and Yemen simmered between Iranian-backed groups and Israel or the United States. Analysts have said Tehran may still hope to avoid being pulled into a costly war, while maintaining support for allies that have traded fire with Israeli forces or attacked Israel’s main backer, the United States, in the region, The Post reported.

U.S. and other officials, speaking on the condition of anonymity to discuss sensitive intelligence matters, said earlier this month they expected Iran could respond with attacks on Israeli targets, calculated to avert an even bigger Israeli response, The Post reported. Yet they acknowledged the potential for miscalculation in such a volatile environment.

White House press secretary Karine Jean-Pierre said Thursday that the Biden administration has “communicated to Iran that the U.S. had no involvement in the strike” in Syria. She said the administration warned Tehran not “to escalate further in the region or attack U.S. facilities or personnel.”

Kareem Fahim and Susannah George contributed to this report.