  Many different classes of X-ray sources contribute to the Galactic landscape
at high energies. Although the nature of the most luminous X-ray emitters is
now fairly well understood, the population of low-to-medium X-ray luminosity
(Lx = 10^27-10^34 erg/s) sources remains much less studied, our knowledge being
mostly based on the observation of local members. The advent of wide field and
high sensitivity X-ray telescopes such as XMM-Newton now offers the opportunity
to observe this low-to-medium Lx population at large distances. We report on
the results of a Galactic plane survey conducted by the XMM-Newton Survey
Science Centre (SSC). Beyond its astrophysical goals, this survey aims at
gathering a representative sample of identified X-ray sources at low latitude
that can be used later on to statistically identify the rest of the
serendipitous sources discovered in the Milky Way. The survey is based on 26
XMM-Newton observations, obtained at |b| < 20 deg, distributed over a large
range in Galactic longitudes and covering a summed area of 4 deg2. The flux
limit of our survey is 2 x 10-15 erg/cm^2/s in the soft (0.5 - 2 keV) band and
1 x 10^-14 erg/cm^2/s in the hard (2 - 12 keV) band. We detect a total of 1319
individual X-ray sources. Using optical follow-up observations supplemented by
cross-correlation with a large range of multi-wavelength archival catalogues we
identify 316 X-ray sources. This constitutes the largest group of
spectroscopically identified low latitude X-ray sources at this flux level. The
majority of the identified X-ray sources are active coronae with spectral types
in the range A - M at maximum distances of ~ 1 kpc. The number of identified
active stars increases towards late spectral types, reaching a maximum at K.
(abridged)
