  We report the detection of a new gamma-ray source in the Fermi-LAT sky using
a source detection tool based on the Minimal Spanning Tree algorithm. The
source, not reported in previous LAT catalogues but very recently observed in
the X-rays and optical bands, is characterized by an increasing gamma-ray
activity in 2012 June-September, reaching a weekly peak flux of
(3.3+-0.6)*10^-7 photons cm^-2 s^-1. A search for a possible counterpart
provides indication that it can be associated with the radio source NVSS
J141828+354250 whose optical SDSS colours are typical of a blazar.
