The US virtual embassy in Iran warned of possible flight cancellations and airspace closures in a security alert urging Americans to depart immediately. “Do not travel to Iran for any reason. US citizens should leave Iran now,” it said in a statement on its website.

The alert cited hostilities between Yemen’s Iran-backed Houthis and Saudi Arabia, including attacks affecting civilian airports, and warned that the conflict “has the potential to escalate rapidly.” It advised Americans to exercise heightened vigilance and check directly with airlines for departure information.

The US also issued warnings on Saturday for Americans in nine countries: Iraq, Bahrain, Oman, Saudi Arabia, Iran, Qatar, Lebanon, Kuwait and Jordan. Its broader regional advisory urged Americans outside the Middle East to seriously reconsider travel to or through the region. It warned that Iran and groups supporting it could target US interests worldwide, including businesses and other institutions.