, Oct. 19 -- The United States has urged its citizens in the Middle East to exercise heightened vigilance amid a complex security situation, warning of possible flight cancellations, airspace closures and travel disruptions.

In a security advisory on Monday, the Department of State said Iranian-supported Houthis have engaged in hostilities against Saudi Arabia, including attacks on civilian airports and other critical infrastructure resulting in civilian casualties and severe travel disruptions.

It warned that the hostilities could escalate rapidly beyond the immediate area.

US citizens travelling to or from the Middle East have been advised to monitor airport and airline operations and make contingency plans in advance.

The advisory ...