Supernovae and other types of transients occurring in the nuclei of galaxies are challenging to find and study, but they offer an opportunity to peek into the surroundings of the supermassive black holes. We will present our systematic search for nuclear transients in the OGLE and Gaia Surveys, both in the archival and real-time data and discuss ways of rapid and machine-learning assisted early classification of transients. We investigated about 20 unusual transients out of hundreds detected. Among discovered objects, there were supernovae and candidates for tidal disruption events (OGLE16aaa, Gaia16aax). We also found examples of unusually long and luminous flares, which could either be supernovae interacting with the interstellar medium or new types of flaring phenomena related to the supermassive black hole.