Belgium has set up a new system to track mobile phones in order to limit crowding of seaside resorts and beaches that formally open for the summer season tomorrow.

Belgium's coastal towns are not seeking to bar tourists from coming, but do want them to use common sense, such as rerouting to a less busy spot or choosing to shop later.

The 10 districts along the coast will detect mobile phones on beaches and the nearby dikes and seafronts and display the live information on a website, with codes from dark green for calm to orange for very busy.