1. A method for tracking objects in a scene being viewed by a sequence of digital images, said method comprising: separating a region of interest in the digital images into a plurality of spatially smaller, overlapping modules, defining a hidden Markov model for each module, said hidden Markov model having a state space describing a grid of centre points of objects within the module, observing detections of positions of possible objects at different times by performing image analysis of the sequence of images, considering a set of states at a point of time (t 1 ) such that the set of states comprises a state having a global optimum probability, and backtracking through the sequence of digital images for each hidden Markov model to shrink the set of states that are possible for earlier parts of the sequence of digital images, such that a single optimal state is found for an earlier point of time (t 2 <t 1 ), whereby tracks of detected objects through the scene are determined up to the earlier point of time (t 2 ).