A closure device for closing a container, including a coupling member with an external thread and a cap with an internal thread intended to be positioned on the coupling member or to be removed from the coupling member by screwing or unscrewing. The closure device also includes security features with at least one circumferential locking stop and at least one locking tab that is radially deformable between a rest position in which the tab cooperates with the circumferential locking stop to prevent unscrewing of the cap and at least one retracted position for releasing the tab relative to the circumferential stop. The tab is carried by the coupling member, and the circumferential stop is carried by the cap.
