  The Large Area Telescope (LAT) onboard the {\it Fermi} Gamma Ray Space
Telescope has detected \gamma-ray emission from some Narrow Line Seyfert
1(NLSy1) galaxies. This indicates the presence of relativistic jets in these
sources similar to blazars and radio galaxies. In an attempt to have an idea of
the intranight optical variability (INOV) characteristics of these \gamma-ray
loud NLSy1 galaxies, we have carried out optical flux monitoring observations
of three NLSy1 galaxies detected by {\it Fermi}/LAT: 1H 0323+342, PMN
J0948+0022 and PKS 1502+036. These optical monitoring observations showed the
presence of rapid optical flux variations in these sources. The intranight
differential light curves of these sources have revealed flux variations on
time scales of hours with amplitudes of variability > 3 percent for most of the
time. On using the {\it F}-statistics to classify the variability nature of
these sources, we obtained a duty cycle (DC) of INOV of ~85 percent.
Alternatively, the more commonly used {\it C}-statistics gave a DC of INOV of
~57 percent. Such high DC of INOV are characteristics of the BL Lac class of
AGN. The results of our monitoring observations thus indicate that there is
similarity in the INOV nature of \gamma-ray loud NLSy1 galaxies and BL Lac
objects, arguing strongly for the presence of relativistic jets aligned closely
to the observers line of sight. Moreover, our dense monitoring observations on
some of the nights have led to the clear detection of some mini-flares
superimposed on the flux variations during the night over timescales as short
as 12 minutes. The detection of short timescale flux variability in the sources
studied here is clearly due to stronger time compression leading to the jets in
these sources having large Doppler factors, similar to that of the inner jets
of TeV blazars.
