Abstract: Anti-theft device comprising a flexible and deformable elongated assembly (1) which is capable of forming a loop and is provided at one end with a male closure member (2, 64) and at the other end with a female closure member (3, 2) adapted to receive and releasably lock the male closure member (2, 64). One of the closure members (3, 62; 2, 64) is provided with a closure device which can be opened by a key in order to release the other closure member. The elongated assembly (1) is made up of elongated elements (8, 41) undetachably assembled together in interengaged relation in the form of a chain.