  We have obtained deep spectroscopic observations of several nearby gamma-ray
burst (GRB) host galaxies revealing for the first time the presence of
Wolf-Rayet (WR) stars and numerous O stars located in rich and compact clusters
or star forming regions. Surprisingly, high spatial resolution imaging shows
that the GRBs and the associated supernovae did not occur in these regions, but
several hundreds of parsec away. Considering various scenarios for GRB
progenitors, we do not find any simple explanation of why they should be
preferentially born in regions with low stellar densities. All the examined
GRBs and associated SNe have occurred 400 to 800 pc from very high density
stellar environments including large numbers of WR stars. Such distances can be
travelled through at velocities of 100 km/s or larger, assuming the travel time
to be the typical life time of WR stars. It leads us to suggest that GRB
progenitors may be runaway massive stars ejected from compact massive star
clusters. The ejection from such super star clusters may lead to a spin-up of
these stars, producing the loss of the hydrogen and/or helium envelopes leading
to the origin of the type Ibc supernovae associated with GRBs. If this scenario
applies tocd text/Sc all GRBs, it provides a natural explanation of the very
small fraction of massive stars that emit a GRB at the end of their life. An
alternative to this scenario could be a binary origin for GRBs, but this still
requires an explanation of why it would preferentially occur in low stellar
density regions.
