The documents relate to several hundred pieces which Nazi officials seized from Jewish families.

The Russian move follows an international conference organised by the United States in Washington this week where delegates from 44 countries also agreed to set up a central registry on art looted by the Nazis which could be established on the Internet.

Nazis stole billions of dollars of art from Jews

Russia has released three sets of previously classified documents including a list of stolen art-works sent to Austrian museums and information on a substantial number of paintings that were confiscated from three major Austrian-Jewish collectors in the 1930s and 40s.

Missing paintings include works by old masters such as Picasso and Cezanne and some of the works are thought to have gone directly to Adolf Hitler's personal museum.

The decision to release the documents represents something of a policy reversal by Russia, which still argues that paintings seized by Soviet soldiers from Nazis in 1945 were legitimately taken as war reparations, and should not be handed back.

Germany also announced that any work now owned by the government which had been taken from a Holocaust victim could be returned to the survivors or their successors.

While senior American officials have welcomed the move, some Jewish leaders say it is merely cosmetic, an attempt to deflect attention from vast bulk of art-work still held in Russia.

Missing billions

It is estimated that around 80% of Jewish art stolen during the war was taken to the Soviet Union - a haul of treasure valued at between $10 and $30bn.

Ronald Lauder from the Museum of Modern Art in New York, also heads the World Jewish Congress's art recovery commission and says every institution, art museum and private collection has some of the estimated 110,000 missing works.

Stuart Eizenstadt, who heads the US delegation that organised this week's conference, observed that Russia had yet to open up its own vast war-time archives to investigators - archives which could well reveal the whereabouts of hundreds of thousands of stolen artworks.

But he said it represented a moral commitment to trace and return stolen art.

"From now on, the sale, purchase, exchange and display of art from this period will be addressed with greater sensitivity and a higher international standard of responsibility," he said.