A bone anchoring device is provided includingan 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), andan 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.
