A bone anchoring device is provided including an anchoring element (1) comprising a shank (2) to be anchored in a bone or a vertebra, a receiving part (4) connected to the shank the receiving part comprising a first end (5) opposite to the shank and a second end (6) facing the shank, a longitudinal axis (L) passing through the two ends, a bore (7) coaxial with the longitudinal axis extending from the first end through at least a portion of the receiving part and a substantially U- shaped recess (10) for receiving a rod (20), the recess forming two free legs (11,12) extending in the direction of the first end, the legs being provided with an internal thread (13), a locking device (3050) for securing the rod in the receiving part said locking device comprising: an external thread (3555) cooperating with the internal thread (13), and an engagement structure (38) provided at the circumference of at least a part of the outer surface projecting above the first end (5) of the receiving part, the structure being engageable with a tool in a form-fit manner and wherein a maximum outer diameter of said locking device in the region of said structure (38) is larger than the inner diameter of the internal thread (13) of the receiving part.
