Vandals have damaged more than 70 artworks and artifacts at some of Berlin's most renowned museums, police said Wednesday, in a targeted attack kept quiet by authorities for more than two weeks. 

Valuable paintings, stone sculptures and sarcophagi at three institutions on the German capital's UNESCO-listed Museum Island were sprayed with an "oily liquid", leaving visible stains, Berlin police told AFP.

German media called it "one of the biggest attacks on art and antiquities in German post-war history".