The US State Department on Sunday urged “extreme caution” at all major airports in Saudi Arabia, following attacks on King Khalid International Airport in Riyadh the day before.

The US Mission strongly recommends all US citizens avoid the airport in the Saudi capital and surrounding areas, according to a security alert.

“US government employees working in Saudi Arabia require special authorization to use the King Khalid International Airport in Riyadh, as well as the airports in Jeddah and Dammam. Please take extreme caution when using all major airports in Saudi Arabia,” it said.

“US citizens should be aware of potential flight cancellations, airspace closures, and travel disruptions,” it continued.

Meanwhile, the Federal Aviation Administration (FAA) told US airlines on Sunday to exercise caution when flying to or over Saudi Arabia, citing safety threats tied to ongoing military activity and interference with navigation systems, according to a report by Reuters.

“Threats could pose a potential risk to aircraft at all altitudes, including overflight, the arrival, and departure phases of flight,” the FAA was quoted as saying, warning of the “potentially hazardous situation.”

The latest warnings came after a Houthi attack on King Khalid International Airport in Riyadh on Saturday killed 12 people and injured 309 others.