The US State Department on Monday issued an alert urging American citizens around the world to "exercise increased caution" over the war with Iran.

The alert said that "due to heightened tensions in the Middle East, the security environment remains complex with the potential for unforeseen escalation."

"Americans outside the Middle East should reconsider travel to and through the region," it said, while warning of the heightened possibility of attacks targeting US diplomatic facilities "or at locations associated with the United States and Americans throughout the world."