A closure device designed to be put in place on, or removed from, a container, including a cap carrying at least two security projections, each provided with an axial locking abutment that can be moved radially between a cooperation position, in which the axial locking abutment engages with an axial locking abutment carried by the container, in order to hold the cap on the container, and a separation position, in which the axial locking abutment is separated from the axial locking abutment carried by the container. The closure device further includes a security ring snap-fitted onto the cap. The security projections are arranged on an internal surface of the security ring and the radial position of each axial locking abutment changes, by ovalization, from its cooperation position to its separation position.
