  The high redhsift blazars powered by supermassive black holes with masses
exceeding $10^9\:M_\odot$ have the highest jet power and luminosity and are
important probes to test the physics of relativistic jets at the early epochs
of the Universe. We present a multi-frequency spectral and temporal study of
high redshift blazar PKS 0537-286 by analyzing data from Fermi-LAT, NuSTAR
Swift XRT and UVOT. Although the time averaged $\gamma$-ray spectrum of the
source is relatively soft (indicating the high-energy emission peak is below
the GeV range), several prominent flares were observed when the spectrum
hardened and the luminosity increased above $10^{49}\:{\rm erg\:s^{-1}}$. The
X-ray emission of the source varies in different observations and is
characterised by a hard spectrum $\leq1.38$ with a luminosity of
$>10^{47}\:{\rm erg\:s^{-1}}$. The broadband spectral energy distribution in
the quiescent and flaring periods was modeled within a one-zone leptonic
scenario assuming different locations of the emission region and considering
both internal (synchrotron radiation) and external (from the disk, broad-line
region and dusty torus) photon fields for the inverse Compton scattering. The
modeling shows that the most optimistic scenario, from the energy requirement
point of view, is when the jet energy dissipation occurs within the broad-line
region. The comparison of the model parameters obtained for the quiescent and
flaring periods suggests that the flaring activities are most likely caused by
the hardening of the emitting electron spectral index and shifting of the
cut-off energy to higher values.
