This paper presents a new image-based approach to the control of a robotic system equipped with an ultra- sound imaging device. For diagnostic applications, the proposed method makes it possible to position an ultrasound probe on a desired organ section and to track it by compensating for rigid motions of the organ. Both in-plane and out-of-plane motions of the probe are controlled by the proposed method. The main contribution of this work is the direct use of the ultrasound image as visual feature which spares any segmentation or image processing time consuming step. Simulation and robotic experiments are performed on a realistic abdominal phantom and validate this ultrasound intensity-based visual servoing approach.