Suturing elements for connecting a vascular prosthesis to a blood vessel include an internal, substantially annular body intended to be received in the blood vessel in addition to an external annular body intended to lie clampingly on an outer wall of the blood vessel at least practically at the location of the internal annular body. At least one of the two annular bodies is provided with suturing members which grip in the vessel wall so as to effect an adequate fixation of at least the internal annular body. The device for use with such suturing elements and a vascular prosthesis which is provided on at least one of its outer ends with at least a part of such suturing elements are disclosed. Different embodiments of such prostheses together form a modular vascular prosthesis system. A side vessel of a thus supported blood vessel can be preserved using branch elements.