The U.S. Embassy in Qatar warned American citizens to "shelter in place until further notice," as Iran vows to hit back against the U.S. for its strikes on nuclear facilities. The embassy said in its June 23 alert that it was acting "out of an abundance of caution" but gave no other details.

The U.S. embassy in Qatar emailed a message to U.S. citizens in the Gulf country on Monday recommending that they shelter in place until further notice.