Prosecutors in Russia's second-largest city of St. Petersburg are investigating reports that unknown men removed a 100-year old bas relief depicting the mythical demon Mephistopheles from the facade of a historical building.

The disappearance of the bas relief, which overlooked the nearby construction site of a new Orthodox church, raised fears of a growing religious intolerance in Russia. A conservative group on Thursday claimed responsibility for the removing the work of art, saying that they set out to eradicate "a cult of Satan."

The prosecutor's office in St. Petersburg issued a statement late on Thursday saying that it has opened an official investigation and seeking those suspected of destroying or damaging a cultural heritage object.