  We present the results of flux density, spectral index, and polarization
intra-night monitoring studies of a sample of eight optically bright blazars,
carried out by employing several small to moderate aperture (0.4\,m to 1.5\,m
diameter) telescopes fitted with CCDs and polarimeters located in Europe,
India, and Japan. The duty cycle of flux variability for the targets is found
to be $\sim 45$ percent, similar to that reported in earlier studies. The
computed two-point spectral indices are found to be between 0.65 to 1.87 for
our sample, comprised of low- and intermediate frequency peaked blazars, with
one exception; they are also found to be statistically variable for about half
the instances where `confirmed' variability is detected in flux density. In the
analysis of the spectral evolution of the targets on hourly timescale, a
counter-clockwise loop (soft-lagging) is noted in the flux-spectral index plane
on two occasions, and in one case a clear spectral flattening with the
decreasing flux is observed. In our data set, we also observe a variety of
flux-polarization degree variability patterns, including instances with a
relatively straightforward anti-correlation, correlation, or counter-clockwise
looping. These changes are typically reflected in the flux-polarization angle
plane: the anti-correlation between the flux and polarization degree is
accompanied by an anti-correlation between the polarization angle and flux,
while the counter-clockwise flux-PD looping behaviour is accompanied by a
clockwise looping in the flux-polarization angle representation. We discuss our
findings in the framework of the internal shock scenario for blazar sources.

High Energy Astrophysical Phenomena