  Naked singularity occurs in the gravitational collapse of an inhomogeneous
dust ball from an initial density profile which is physically reasonable. We
show that explosive radiation is emitted during the formation process of the
naked singularity. The energy flux is proportional to $(t_{\rm CH}-t)^{-3/2}$
for a minimally coupled massless scalar field, while is proportional to
$(t_{\rm CH}-t)^{-1}$ for a conformally coupled massless scalar field, where
$t_{\rm CH}-t$ is the `remained time' until the distant observer could observe
the singularity if the naked singularity was formed. As a consequence, the
radiated energy grows unboundedly for both scalar fields. The amount of the
power and the energy depends on parameters which characterize the initial
density profile but do not depend on the gravitational mass of the cloud. In
particular, there is characteristic frequency $\nu_{s}$ of singularity above
which the divergent energy is radiated. The energy flux is dominated by
particles of which the wave length is about $t_{\rm CH}-t$ at each moment. The
observed total spectrum is nonthermal, i.e., $\nu dN/d\nu \sim
(\nu/\nu_{s})^{-1}$ for $\nu>\nu_{s}$. If the naked singularity formation could
continue until a considerable fraction of the total energy of the dust cloud is
radiated, the radiated energy would reach about $10^{54}(M/M_{\odot})$ erg. The
calculations are based on the geometrical optics approximation which turns out
to be consistent as a rough order estimate. The analysis does not depend on
whether or not the naked singularity occurs in its exact meaning. This
phenomenon may provide a new candidate for a source of ultra high energy cosmic
rays or a central engine of gamma ray bursts.
