The U.S. State Department on Sunday issued a Worldwide Caution Security Alert, advising U.S. citizens overseas to exercise increased caution.

"The conflict between Israel and Iran has resulted in disruptions to travel and periodic closure of airspace across the Middle East," said the notice posted on the State Department's website.

"There is the potential for demonstrations against U.S. citizens and interests abroad. The Department of State advises U.S. citizens worldwide to exercise increased caution," it said.

The United States struck three key nuclear facilities in Iran on Saturday, claiming that it had obliterated Iran's nuclear program.

Late Saturday night, U.S. President Donald Trump warned that any retaliation by Iran against the United States "will be met with force far greater than what was witnessed tonight."

The State Department last week warned U.S. travelers not to travel to Israel, Gaza and the West Bank because of armed conflict, terrorism and civil unrest.