  We have conducted a new spectroscopic survey to characterize the nature of
nuclear activity in Hickson Compact Groups (HCGs) galaxies and establish its
frequency. We have obtained new intermediate resolution optical spectroscopy
for 200 member-galaxies and corrected for underlying stellar population
contamination using galaxy templates. Spectra for 11 additional galaxies have
been acquired from the ESO and 6dF public archives and emission line ratios
have been taken from the literature for 59 galaxies more. Here we present the
results of our classification of the nuclear activity for 270 member-galaxies,
which belong to a well defined sample of 64 HCGs. We found a large fraction of
galaxies, 63%, with emission lines. Using standard diagnostic diagrams, 45% of
the emission line galaxies were classified as pure AGNs, 23% as Transition
Objects (TOs) and 32% as Star Forming Nuclei (SFNs). In the HCGs, the AGN
activity appears as the most frequent activity type. Adopting the
interpretation that in TOs a Low Luminosity AGN coexists with circumnuclear
star formation, the fraction of galaxies with an AGN could rise to 42% of the
whole sample. The low frequency (20%) of SFNs confirms that there is no star
formation enhancement in HCGs. After extinction correction we found a median
AGN H$\alpha$ luminosity of 7.1$\times10^{39}$ erg s$^{-1}$, which implies that
AGNs in HCG have a characteristically low luminosity. This result added to the
fact, that there is an almost complete absence of Broad Line AGNs in Compact
Groups (CGs) as found by Martinez et al.(2008a) and corroborated in this study
for HCGs, is consistent with very few gas left in these galaxies. In general,
therefore, what may characterize the level of activity in CGs is a severe
deficiency of gas.
