BERLIN (AFP) - US and British heirs of Nazi-era Jewish art dealers have sued Germany for the return of a mediaeval art treasure worth US$250-300 million (S$312-375 million euros), their lawyers said on Tuesday.
At stake in the case filed on Monday before a US district court in Washington is the Guelph Treasure or "Welfenschatz" of more than 40 gold, silver and gem-studded church relics.
The suit, the latest twist in a legal tussle dating back to 2008, targets the German government and the Prussian Cultural Heritage Foundation, which is exhibiting the collection in a Berlin museum.
The US lawyers, presenting their case in Berlin on Tuesday, said four Jewish collectors had to sell the artworks in a "sham transaction" far below their fair market price in 1935 under duress from the Nazis.
"The Jewish people who owned this art had their property squeezed out of them while their lives and the lives of their families were at risk," said US lawyer Nicholas O'Donnell.
The lawsuit argues that "such transactions in Nazi Germany were by definition coercive, voidable and should not be considered valid".
Germany has argued the four dealers received a fair market price from the state of Prussia then led by Hermann Goering, the Gestapo secret police founder and air force chief.
In March last year Germany's advisory body on cases of suspected Nazi-looted art, the Limbach Commission, said it saw no evidence of "a persecution-induced forced sale" and that the price was normal following the 1929 Wall Street crash.
The panel, whose rulings are non-binding, argued that in 1935 all sides had voluntarily consented to the deal for the treasure, which was then being held out of the Nazis' reach in Amsterdam.
The foundation said on Tuesday it was "surprised and disappointed" by the lawsuit, saying it was unaware of any new evidence that would justify revisiting the commission's recommendation.
The Guelph Treasure, now exhibited in Berlin's Museum of Decorative Arts, originally numbered over 80 pieces dating from the 11th to 15th centuries.
The Duke of Brunswick sold off the collection in 1929, with many pieces bought by the Jewish consortium.
The city-state of Berlin said last week it had placed the Guelph Treasure, the largest publicly owned collection of German ecclesiastical art, under national heritage protection, meaning it may only leave the country with permission of the minister for culture.