  We study the probability of close encounters between stars from a nuclear
cluster and a massive black hole. The gravitational field of the system is
dominated by the black hole in its sphere of influence. It is further modified
by the cluster mean field (a spherical term) and a gaseous disc/torus (an
axially symmetric term) causing a secular evolution of stellar orbits via Kozai
oscillations. Intermittent phases of large eccentricity increase the chance
that stars become damaged inside the tidal radius of the central hole. Such
events can produce debris and lead to recurring episodes of enhanced accretion
activity. We introduce an effective loss cone and associate it with tidal
disruptions during the high-eccentricity phases of the Kozai cycle. By
numerical integration of the trajectories forming the boundary of the loss cone
we determine its shape and volume. We also include the effect of relativistic
advance of pericentre. The potential of the disc has the efffect of enlarging
the loss cone and, therefore, the predicted number of tidally disrupted stars
should grow by factor of ~10^2. On the other hand, the effect of the cluster
mean potential together with the relativistic pericentre advance act against
the eccentricity oscillations. In the end we expect the tidal disruption events
to be approximately ten times more frequent in comparison with the model in
which the three effects -- the cluster mean field, the relativistic pericentre
advance, and the Kozai mechanism -- are all ignored. The competition of
different influences suppresses the predicted star disruption rate as the black
hole mass increases. Hence, the process under consideration is more important
for intermediate-mass black holes, M_bh~10^4M_s.
