Despite government efforts to track down stolen artwork, only two pieces from federal collections have been returned to legal heirs since 1998.
Tuesday, Germany's federal cultural minister called on more than 5,300 German museums and libraries to intensify their efforts to identify and return treasures illegally appropriated during World War II.
Julian Nida-Ruemelin stressed that Germany is far from the "end phase in dealing with its Nazi past" as some had hoped would be the case by the end of the 20th century.
"Those commentators were mistaken," he said. "The attention is larger than ever before."
He noted that there was a moral obligation to return the artwork even though legal claims had expired in many cases.
In stressing the need for German public institutions to double-check art inventories, Stephan Articus, head of the German Council of Cities, noted, "The cities where Nazis committed these wrongs carry a special responsibility."
The government has set up a Website listing about 17,000 works of Nazi-looted art currently displayed in public collections.
Another 23,000 works are currently being cataloged for the database. The site also lists more than 2,200 pieces that were seized by U.S. troops at the end of the war that are being held in Munich. Private citizens can also access the database about works stolen from personal collections.
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