The US State Department issued a worldwide security alert Sunday urging American citizens, particularly those in the Middle East, to exercise "increased caution."

The agency warned that groups supportive of Iran may target US interests and locations associated with Americans around the world.

The alert said US diplomatic facilities outside the Middle East had already been targeted and warned of periodic airspace closures causing travel disruptions.

Americans abroad were urged to follow guidance from the nearest US embassy or consulate.

The warning came as US-Israeli strikes against Iran entered their fourth week, with Tehran retaliating with drone and missile strikes targeting Israel, Jordan, Iraq and Gulf countries hosting US military assets.

The strikes began on Feb. 28 and have reportedly killed at least 1,300 people, including then-Supreme Leader Ayatollah Ali Khamenei.