BERLIN (AFP).- Identifying the rightful owners of a vast trove of art looted by the Nazis will be an enormous task potentially complicated by the German authorities' insistence on discretion, experts said Wednesday.

The more than 1,400 artworks found last year stashed in the Munich apartment of Cornelius Gurlitt, son of a powerful Nazi-era art dealer, represent perhaps the largest discovery of missing 20th century art in Europe since World War II.

But beyond its scope, its richness is staggering, with masterpieces by Picasso, Matisse and Renoir along with previously unknown works by modernist painters Marc Chagall and Otto Dix among its gems.

Focus, the magazine that broke the story this week, estimated the value of the collection at one billion euros ($1.3 billion), a figure German investigators have declined to confirm.

The German government and state prosecutors in the southern city of Augsburg assume that the Nazis stole the art from Jewish collectors, bought it from them for a pittance under duress, or seized it from museums as part of a crackdown on avant-garde "degenerate art".

Gurlitt's father Hildebrand was one of a handful of dealers tasked by Nazi propaganda chief Joseph Goebbels with selling such works abroad in exchange for hard currency.

The Holocaust Art Restitution Project posted a list on its Facebook page Wednesday of artworks seized from Hildebrand Gurlitt by US forces immediately after World War II that were returned to him in 1950 after intensive lobbying.

Many of the paintings appear to be those found in the Munich apartment last year.

Because of the complexity of the research, Berlin has dispatched experts in Nazi-era looted and banned art to assist a sole art historian assigned by the Augsburg prosecutors in charge of the investigation to catalogue the works.

They say they have opted not to publish a full inventory of what was found in Gurlitt's rubbish-strewn flat in February 2012 because it could violate the privacy rights of those asserting ownership and trigger a flood of frivolous claims.

However Chancellor Angela Merkel's spokesman Steffen Seibert, while stressing that the prosecutors were responsible for the probe, noted the moral obligation Germany had to reveal what it knows about the hoard.

"The federal government is pushing with urgency, independent of the criminal inquiry, for information on confiscated artworks to be published for which there is already evidence that they were seized as part of Nazi persecution," he told reporters.

Robbed by the Nazis

Untangling their provenance will be complicated legal terrain, a specialist on restitution issues, Vanessa-Maria Voigt, said.

"If it is proven that Cornelius Gurlitt inherited (these works), he is an heir like any other and can hold onto the paintings," Voigt, who is based at the main municipal art museum in Munich, told AFP.

"There have been cases of restitution by individual people, but on a voluntary basis."

During a news conference Tuesday at which slides of some of the Munich artworks were presented, Augsburg chief prosecutor Reinhard Nemetz put the onus on "those who think they lost artwork under the Nazi regime" to come forward.

"Heirs, including the families robbed by the Nazis, can try to make legal claims," another restitution expert, Imke Gielen, told the daily Frankfurter Allgemeine Zeitung.

But she noted that such procedures can be lengthy, complex and unpredictable.

A Washington accord dating from 1998 covering art taken from Jews under the Nazis commits public institutions and large museums to do their utmost to return work to their rightful owners or their heirs.

But Julian Radcliffe, chairman of the Art Loss Register, which maintains a database of stolen and missing works, told AFP this week that the art market often played by different rules.

"If everybody in the art trade checked everything that they bought or sold, it would stop these pictures ever getting into the legitimate market," he said.

"That's our job, and we've got to do that for the next 200 years."



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