  The observation of a strong and extended positron-electron line annihilation
emission in the central regions of the Galaxy by INTEGRAL-SPI, consistent with
the Galactic bulge geometry, without any counterpart in the gamma-ray range,
neither at high energy nor in the 1809 keV $^{26}$Al decay line, is
challenging. Leaving aside the geometrical question, we address the problem of
the adequate positron sources, showing the potentiality of a new category of SN
Ic, exemplified by SN2003dh, which is associated to a gamma-ray burst. This
kind of supernova/hypernova/GRB event is interpreted as the result of a bipolar
Wolf-Rayet explosion, which produces a large amount of $^{56}$Ni and ejects it
at high velocity along the rotation axis. The bulk of positrons resulting from
$^{56}$Co decay escapes in the surrounding medium due to the rapid thinning of
the ejecta in the polar direction. We show that a rate of about 0.02
SN2003dh-like events per century in the central region of the Galaxy is
sufficient to explain the positron flux detected by INTEGRAL-SPI. In order to
explain this flux by SN Ia events alone, a rate of 0.5 per century is
necessary, much higher than indicated by Galactic evolutionary models applied
to the bulge. Further observations of late light curves of SNe Ia and SNe Ic in
the bulge of spiral galaxies, together with 3D hydrodynamic calculations of
anisotropic ejections of $^{56}$Ni in SN Ic/GRB events, will allow to estimate
the separate contributions of SNe Ia and SNe Ic to positron injection.
