This article introduces a system for real-time people counting. People counting systems are challenging in the surveillance domain. The proposed system is built from INT3-Horus, a multi-agent based framework for intelligent monitoring and activity interpretation. The system uses an indoor overhead video camera that detects people moving freely in a hall or room. The people counting system is flexible in detecting individuals as well as groups. Counting is independent of the trajectories and possible occlusions of the humans present in the scene. The initial results offered by the system are very promising in terms of specificity, sensitivity and F-score.