  The gamma-ray bursts (GRBs) of long duration are very likely to be connected
to the death of massive stars. The gamma-ray emission is believed to come from
energy released internally in a flow that moves at ultrarelativistic speed. The
fast flow drives a shock wave into the external medium leading to the afterglow
emission. Most massive stars form in dense clusters, their high luminosity
producing a very dense radiation field. Here, I explore the observational
consequences of the interaction of the shocked external medium of the burst
with the photon field of a nearby O star. I show that inverse Compton
scattering of the stellar photons by electrons heated by the shock leads to
powerful gamma-ray emission in the ~1-100 GeV range. This emission appears
minutes to hours after the burst and can be easily detected by Cherenkov
telescopes and probably with the GLAST satellite. This signal may have already
been observed in GRB 940217 and can yield important information about the
circumburst environment and the extragalactic background light.
