We present the results of our near-infrared spectroscopic program of Trans-Neptunian objects (TNOs), Centaurs and comet nuclei. TNOs, centaurs, and Jupiter family (JF) comets are three intimately related populations of minor planet bodies originated in the outer solar system. They probably contain some of the least modified materials remaining from the protosolar nebula. The study of their physical properties and evolution provide invaluable cosmogonical information. Near-infrared spectroscopy is a diagnostic method for remote determination of the surface composition of these objects. Taking advantage of the unique high efficiency, very low resolution mode of the new Near Infrared Camera Spectrograph (NICS) instrument installed at the 3.56m italian Telescopio Nazionale Galileo (TNG, Roque de los Muchachos Observatory, Canary Islands, Spain), we started a program to obtain low resolution spectra of these objects late 2000. In this mode a prism-based optical element, the Amici device, is used to obtain in the detector a complete 0.85-2.45 microns long slit spectrum of the astronomical source, with an approximately constant resolving power R 50, when the 1" slit is used. In addition to the already published spectra of (38628) Huya and (20000) Varuna (Licandro et al. 2001, A&A 373, 29L), and (28978) Ixion (Licandro et al. 2002, A&A 388, 9L) and 124P/Mrkos (Licandro et al. 2003, A&A 398, 45L) we present new spectra of the TNOs (38628) Huya, (50000) Quaoar, and 1999 TC36, and the Centaurs (8405) Asbolus, (54598) 2000 QC243,(32532) Thereus, (31824) Elatus, and 2002 PN34. Results on comet 28P/Neujmin 1 will be also presented by Campins et al. (this conference). Water ice absorption bands are present in the spectra of several objects. Evidence of surface inhomogeneities is also presented, in particular in the case of (32532) Thereus that was observed during an almost complete rotation. The results are discussed in the framework of the possible resurfacing mechanisms proposed (space weathering, coma activity and collisions).