Provided is a surgical instrument including an external tube (2) and two elongated members (4) positioned in the tube (2), each of which includes a distal end (10a) for capturing one of the two tissue zones (M1, M2) to be attached. The instrument (1) may further include a catching member (22, 25) for each tissue (M1, M2) to be attached; a rod (15, 16) linked to each catching member (22, 25) enabling tension to move axially, the rod (15, 16) being separable from said catching member (22, 25) when a tension is exerted on it beyond a certain threshold; and a member (17a) forming a stop for locking axially each catching member (22, 25) during the tensioning.