  We identified Active Galactic Nuclei (AGN) candidates as counterparts to
unidentified gamma-ray sources (UGS) from the Fermi-LAT Fourth Source Catalogue
at lower Galactic latitudes. Our methodology is based on the use of near- and
mid-infrared photometric data from the VISTA Variables in the V\'ia L\'actea
(VVV) and Wide-field Infrared Survey Explorer (WISE) surveys. The AGN
candidates associated with the UGS occupy very different regions from the stars
and extragalactic sources in the colour space defined by the VVV and WISE
infrared colours. We found 27 near-infrared AGN candidates possibly associated
with 14 Fermi-LAT sources using the VVV survey. We also found 2 blazar
candidates in the regions of 2 Fermi-LAT sources using WISE data. There is no
match between VVV and WISE candidates. We have also examined the K$_\mathrm{s}$
light curves of the VVV candidates and applied the fractional variability
amplitude ($\mathrm{\sigma_{rms}}$) and the slope of variation in the
K$_\mathrm{s}$ passband to characterise the near-infrared variability. This
analysis shows that more than 85% of the candidates have slopes in the
K$_\mathrm{s}$ passband $ > 10^{-4}$ mag/day and present
$\mathrm{\sigma_{rms}}$ values consistent with a moderate variability. This is
in good agreement with typical results seen from type-1 AGN. The combination of
YJHK$_\mathrm{s}$ colours and K$_\mathrm{s}$ variability criteria was useful
for AGN selection, including its use in identifying counterparts to Fermi
$\gamma$-ray sources.
