We present new mid-infrared (N-band) images of a sample of eight nearby Sey
fert galaxies. In an of our targets, we, detect a central unresolved source
, which in some cases has been identified for the first time. In particular
, we have detected the mid-infrared emission from the active nucleus of NGC
4945, which previously remained undetected at any wavelength but hard X-ra
ys. We also detect circumnuclear extended emission in the Circinus galaxy a
long its major axis and find marginal evidence for extended circumnuclear e
mission in NGC 3281. The high spatial resolution (1."7) of our data allows
us to separate the flux of the nuclear point sources from the extended circ
umnuclear starburst (if present). We complement our sample with literature
data for a number of nonactive starburst galaxies and relate the nuclear N-
band flux to published hard (2-10 keV) X-ray fluxes. We find tight and well
-separated correlations between the nuclear N-band flux and X-ray flux for
both Seyfert and starburst nuclei that span over 3 orders of magnitude in l
uminosity. We demonstrate that these correlations can be used as a powerful
classification tool for galactic nuclei. For example, we find strong evide
nce against NGC 1808 currently harboring an active Seyfert nucleus based on
its position in the mid-infrared-X-ray diagram. On the other hand, we conf
irm that NGC 4945 is in fact a Seyfert 2 galaxy.