“The conflict between Israel and Iran has resulted in disruptions to travel and periodic closure of airspace across the Middle East. There is the potential for demonstrations against US citizens and interests abroad,” the state department’s security alert said.

“The department of state advises US citizens worldwide to exercise increased caution.”

The statement made no mention of the US intervening in the conflict overnight when American planes bombed nuclear facilities in Iran, a move that Tehran said would have “irreparable consequences.”

The Islamic republic on Sunday threatened US bases in the Middle East and warned that US forces could be attacked in retaliation for the unprecedented air strikes that the Pentagon said devastated Iran’s nuclear programme.

“Any country in the region or elsewhere that is used by American forces to strike Iran will be considered a legitimate target for our armed forces,” Ali Akbar Velayati, an advisor to Iran’s supreme leader Ayatollah Ali Khamenei, said in a message carried by the official IRNA news agency.

The US on Saturday began evacuation flights from Israel for American citizens and permanent US residents living in Israel or the West Bank.

It also ordered staff at its diplomatic missions in Iraq and Lebanon to leave those countries.