"The security situation in Somalia is extremely unstable," the release said, "and the threat to all U.S. citizens in Somalia remains critical."

The U.S. State Department does not have an embassy in the country.

On Friday, U.S. Africa Command acknowledged that it had conducted a pair of airstrikes to target the Islamic State in the northeast part of Somalia. The strikes marked the first time the U.S. military targeted Islamic State militants in the country.