Federal officials are increasingly concerned about the possibility of Iran or its supporters retaliating on American soil after the bombing of nuclear sites in Iran by U.S. forces.

In an internal email on Sunday, top officials at the F.B.I. cautioned that Iran and its proxies have “historically targeted U.S. interests in response to geopolitical events, and they are likely to increase their efforts in the near term.”

They urged field offices to monitor their collection platforms and stay in close contact with the Defense Department, including the National Guard, “who may be targeted for retaliation” while “specific attention should be paid to” U.S. military facilities connected to the strikes in Iran.

In New York City, Mayor Eric Adams said that more police officers would be on duty around religious, cultural and diplomatic sites “out of an abundance of caution,” given the situation in the Middle East.

Iran, which the United States has designated as a state sponsor of terrorism, has long backed a network of militias across the Middle East in an attempt to extend its influence across the region and undermine Israel. Those militias include Hamas, Hezbollah and the Houthis, who control parts of Yemen.

Separately, the Department of Homeland Security issued a security bulletin stating that the “ongoing Iran conflict” had elevated security concerns in the country and adding that cyberattacks by pro-Iranian hackers were likely.