  We present the results of observations of the soft gamma-ray early afterglows
with the energy above 100keV from two bright Gamma-ray bursts detected by the
PHEBUS instrument of the GRANAT orbital observatory. We show that the light
curves of GRB910402 and GRB920723 events present the afterglow emission with
fading fluxes. During our observations ~700s for these gamma-ray bursts the
afterglow emission was fading as the power law of time with indices equal to
-0.70+/-0.04 and -0.60+/-0.05 (at 1sigma confidence level). In both cases just
after the end of the GRB event we observed the energy spectrum of the afterglow
emissions which was softer than the energy spectrum of the main GRB events. The
average photon index of the main GRB event (in 100-800keV range) is equal to
\~1.5. In the beginning of the afterglow emission the energy spectra of both
events correspond to the much softer spectra with the photon index of ~2.5. We
found that the times of abrupt softening of the burst spectra correspond within
statistical errors to the moment when the afterglow emission begins to dominate
over GRB emission. We found that during the afterglow emission of GRB910402 the
statistically significant hardening of its spectra was observed. This is the
first observation of hardening of GRB afterglow emission. Analysis of GRB910402
and its afterglow showed that this GRB source emits during ~700s of our
observations in soft gamma-rays (100-500keV) only ~1.6% of its total energy
released during the main event. For the GRB920723 we found that in afterglow
during ~700s of our observations ~6% of the GRB total energy was released.
