The present invention proposes a warning system that can be implemented in any kind of vehicle, in order to efficiently detect moving objects. The system utilizes at least one camera for a continuous imaging of the surroundings of the vehicle. Thereby, moving objects can be monitored. A computing unit is programmed to estimate a motion of any moving object based on a pixel motion in the camera image. If a dangerously moving object is detected, a warning unit can be used for issuing a warning signal. To take such a decision, the estimated motion of at least one of the moving objects can be correlated or compared to predetermined motion patterns.