An apparatus (10) and a method are described for producing a closing system (100) for containers comprising an anti-tampering strip (101) configured to be attached to an opening of a container, and a re-closable closing body (102), configured to hermetically close said containers. The apparatus (10) comprises a welding and deformation station (11) in which it is provided to weld a barrier element (108) to the re-closable closing body (102) and to fold a flexible annular portion (109) of the anti-tampering strip (101) back toward the inside of the closing system (100) while the latter is stationary in a same predetermined position in the welding and deformation station (11).