Concerns are growing that the conflict between Saudi Arabia and Yemen’s Houthi rebels could escalate and spread across the Middle East, prompting the United States to issue a security alert for its citizens in several countries in the region.

The US State Department issued the warning late Saturday (September 19), local time.

The countries covered by the alert include Israel, Lebanon, Jordan, Iraq, Saudi Arabia, Kuwait, Bahrain, Qatar, the United Arab Emirates (UAE) and Oman.

In its advisory, the State Department urged US citizens currently in the Middle East to exercise maximum caution. It also warned them to remain prepared for flight cancellations, airspace closures and sudden disruptions to travel.

The advisory called on US citizens to avoid traveling to the Middle East. It said Iran-backed Houthis have carried out attacks on various targets, including civilian airports in Saudi Arabia.

The department further warned that the ongoing military confrontation could rapidly escalate into a more serious conflict at any time. It also said Iran and groups aligned with Tehran could target US citizens, businesses, organizations or other facilities linked to US interests anywhere in the world.

Saudi Arabia has reportedly sought assistance from allied countries to counter Houthi attacks on the forces of Yemen’s internationally recognized government.

The US warning comes amid speculation that Washington could launch fresh strikes against Houthi positions in Yemen or against Iran.

Meanwhile, Barak Ravid, a journalist with US news outlet Axios, reported that President Donald Trump had shortened his stay at Camp David. He returned to the White House one day earlier than scheduled.