We have identified two late M dwarfs within 10 pc of the Sun, by cross-correlating the Luyten NLTT catalogue of stars with proper motions larger than 0.18 arcsec/yr, with objects lacking optical identification in the 2MASS data base. The 2MASS photometry was then combined with improved optical photometry obtained from the SuperCOSMOS Sky Surveys. The two objects (LP 775- 31 and LP 655- 48) have extremely red optical-to-infrared colours (R-Ks ~ 7 mag) and very bright infrared magnitudes (Ks < 10 mag): follow-up optical spectroscopy with the ESO 3.6-m telescope gave spectral types of M 8.0 and M 7.5 dwarfs, respectively. Comparison of their near-infrared magnitudes with the absolute magnitudes of known M 8 and M 7.5 dwarfs with measured trigonometric parallaxes yields spectroscopic distance estimates of 6.4+/-1.4 pc and 8.0+/-1.6 pc for LP 775- 31 and LP 655- 48, respectively. In contrast, Cruz & Reid (cite{cruz02}) recently determined spectral types of M 6 for both objects, and commensurately larger distances of 11.3+/- 1.3 pc and 15.3+/- 2.6 pc. LP 655- 48 is also a bright X-ray source (1RXS J044022.8-053020). With only a few late M dwarfs previously known within 10 pc, these two objects represent an important addition to the census of the Solar neighbourhood. Based on observations collected with the ESO 3.6-m/EFOSC2 at the European Southern Observatory, La Silla, Chile (ESO programme 68.C-0664).