  We present the results obtained from a comprehensive timing and spectral
study of two high-mass X-ray binary sources using NuSTAR observations. These
two sources, IGR J16320-4751 and IGR J16479-4514, were discovered by INTEGRAL
and have been characterized for the first time in the hard X-ray band (beyond
10~keV) in this work. In these sources, we observe the occurrence of intense
X-ray flares, with average luminosities exceeding 10$^{36}$~erg~s$^{-1}$. Our
analysis reveals that these flares can be described consistently in the
quasi-spherical accretion regime. The orbital phase of the first flare in
NuSTAR observation of IGR J16479-4514 matches with the orbital phases of
previous flares ($\phi=0.35$) in this source detected by other telescopes. We
conclude that this flare occurs as a result of the periastron passage of the
neutron star, rather than due to the presence of a corotating interaction
region (CIR). Furthermore, from the energy-resolved pulse profile analysis of
IGR J16320-4751, we find that the pulse fraction is lower in hard X-rays
compared to soft X-rays. We present the hard X-ray spectral parameters of these
two sources using several standard spectral model components. We do not detect
a cyclotron absorption feature in either target. We provide estimates of the
surface magnetic field strength of NS in IGR J16320-4751 using two indirect
methods. Lastly, we observe spectral hardening during flaring segments compared
to the off-flaring segments which indicates that comptonization is more
effective during the flaring segments.
