The system (1) comprises: a tubular interface formation (3) fixed or able to be fixed to a receiving body (C) and having a plurality of shaped retaining lugs (4) angularly spaced around its axis (A-A) and protruding axially and radially towards the outside; a tubular fastening member (6) in which the tube (2) can be pre-inserted axially and which has a plurality of external peripheral coupling elements (15) angularly spaced around its axis (A-A) and each able to engage with a corresponding retaining lug (4) of the interface formation (3), in a mutually axially retaining relationship. The fastening member (6), with the tube (2) pre-inserted therein, is able to be inserted into the interface formation (3) in a relative coupling position in which the coupling elements (15) of the fastening member (6) angularly alternate with the retaining lugs (4, 5) of the interface formation (3); the fastening member (6) can then be rotated in a predetermined direction (B), around the tube (2) and with respect to the interface formation (3), from the coupling position into a relative locking position, such as to achieve the engagement of each of its coupling elements (15) with a corresponding retaining lug (4, 5) of the interface formation (3).