The female figurine is thought to be a depiction of the god of fertility, and will be displayed at the Polish Arms Museum
The Kunstverein in Hamburg said the incident is currently being investigated by authorities as a hate crime
Exhibition wants to show the "making of" the nihilist philosopher's personality cult
The painting, Madame Soler, was previously owned by the prominent collector Paul von Mendelssohn-Bartholdy in the 1930s
Use of police forces against supporters of artist Sandro Sulaberidze have been criticised by country's top state officials
The paintings, from the workshop of the Flemish master Dieric Bouts, were transferred from the Museo Provincial de Pontevedra in Spain to Gołuchów Castle
Statement comes after Berlin state secretary for diversity and anti-discrimination spoke out in favour of restituting the artefacts to their countries of origin