An intumescent gasket substantially composed of a profiled body (2) for forming a seal between more than one element (5, 7), obtained by extruding a mixture comprising thermoplastic material, expanding graphite and one or more flame-retardant substances. A flexible reinforcement fabric (3) is internally coupled to the profiled body (2) of the gasket (1) during the extrusion process by means of an extrusion head so that it becomes embedded into the profiled body (2).