  In relativistic strongly magnetized winds outflowing from the fast-rotating
compact progenitors of gamma-ray bursts (GRBs) there are three regions where
powerful high-frequency emission may be generated: (i) the thermal photosphere,
(ii) the region of the internal wind instability and (iii) the region of the
wind interaction with an ambient gas. This results in a multicomponent
structure of GRBs. The emission from the thermal photosphere may be observed as
a weak precursor to the main burst. The precursor should have a blackbody-like
spectrum with the mean energy of photons of $\sim 1$ MeV, and its intensity
should be tens to hundreds of times smaller than that of the main GRB emission.
Observations of such precursors with future $\gamma$-ray missions like GLAST
can clarify the nature of bursters.
