  We present a XMM-Newton observation of Markarian 304, a Seyfert 1 galaxy at z
= 0.066. The EPIC data show that MKN 304 is affected by heavy (Nh ~10^{23}
cm{-2}) obscuration due to ionized gas. A two-phase warm absorber provides an
adequate parameterization of this gas. The ionization parameter of the two
components is \xi ~6 erg/cm2/s and \xi ~90 erg/cm2/s, respectively. The
observed continuum photon index (Gamma ~1.9) is typical for Seyfert 1 galaxies.
Two significant emission lines are detected at 0.57 keV and 6.4 keV,
respectively. The former is mostly likely due to He-like oxygen triplet
emission arising from an ionized plasma (maybe the warm absorber itself). The
latter is due to fluorescent emission of K-shell iron in a low-ionization state
(FeI--XV). The upper limit for the line width of sigma_{K\alpha} <0.18 keV most
likely rules out an origin in the inner parts of the accretion disk.
Interestingly, the strength of such line is consistent with the possibility
that the emission is produced in the warm absorber itself. However, a
substantial contribution from the torus is plausible too. We have also found a
weak (4% of the primary continuum) soft excess emission component. The presence
of this excess could be explained by either emission/scattering from a warm gas
or partial covering, or a combination of them.
