Results of atomistic simulation of (0001) GaN surface bombardment by 50 eV/a.m.u. atomic (F, P, Ag) and molecular (PF[2] and PF[4]) ions are presented. Strong in-cascade recombination of generated point defects is found. Final defect distributionsare significantly shifted towards the surface. Both these findings are in good agreement with experimental data on formation of structural defects in GaN under accelerated ion irradiation. Enhanced defect generation as compared to approximationgiven by binary collisions is found for heavy atomic (Ag) and molecular (PF[4]) ions. In the case of molecular ion the mentioned effect is observed close to the sample surface only.