  The sunspot-associated sources at the frequency of 17 GHz give information on
plasma parameters in the regions of magnetic field about B=2000 G at the level
of the chromosphere-corona transition region. The observations of short period
(from 1 to 10 minutes) oscillations in sunspots reflect propagation of
magnetohydrodynamic (MHD) waves in the magnetic flux tubes of the sunspots. We
investigate the oscillation parameters in active regions in connection with
their flare activity. We confirm the existence of a link between the
oscillation spectrum and flare activity. We find differences in the
oscillations between pre-flare and post-flare phases. In particular, we
demonstrate a case of powerful three-minute oscillations that start just before
the burst. This event is similar to the cases of the precursors investigated by
Sych, R. et al. (Astron. Astrophys., vol.505, p.791, 2009). We also found
well-defined eight-minute oscillations of microwave emission from sunspot. We
interpret our observations in terms of a relationship between MHD waves
propagating from sunspot and flare processes.
