The US Department of State has urged citizens to "exercise caution and heightened vigilance" amid the escalating conflict in the region.

"Worldwide Caution: Due to heightened tensions in the Middle East, the security environment remains complex with the potential for unforeseen escalation," the statement read.

It instructed Americans to be prepared for "flight cancellations, periodic airspace closures, and potential travel disruptions", and cautioned that US facilities across the world may be targeted.