GRBs are nowadays a rather well understood phenomenon in the soft (KeV-MeV) γ-ray energy band, while only a few GRBs have been observed at high photon energies (Eγ >∼1 GeV). It is also widely recognized that GRBs accelerate protons to relativistic energies and that dense media are often present nearby the sources. Within this framework and by further adopting Totani’s suggestion that GRB events release an amount of energy ∼ 10 54 ∆Ω erg, we compute in detail the high-energy γ- ray flux from the decay of neutral pions produced through the interaction of accelerate protons with nucleons in the surrounding medium. We also take into account the local and intergalactic γ-ray absorption. The presence of magnetic fields around the GRB sources causes the deflection of the accelerated protons and so a temporal spread of the produced high-energy γ-rays with respect to the signal in the soft γ-ray band. Moreover, we analyze the possibility to detect the γ-ray signal in the GeV-TeV energy range by the ARGO detector under construction in Tibet