ST. PETERSBURG -- The secret vaults of the Hermitage recently opened a crack, giving the world a tantalizing glimpse of long-lost Impressionist treasures buried inside. But that brief glimpse has also set the stage for a storm of bitter claims and counterclaims to ownership.


The cause of all the furor was an interview that Hermitage director Mikhail Pyotrovsky gave to The New York Times in early October, in which he said that his vast Petersburg museum planned to mount an exhibit in March of Impressionist and Postimpressionist paintings that had been hidden in the museum for over 50 years.


"I don't know what all the fuss is about," complained Pyotrovsky. "It seems that nothing is news in the West until it's on the front page of The New York Times."


But if art journalist Konstantin Akinsha is to be believed, the Hermitage is sitting on one of the richest collections of Impressionist art in the world.


"The contents of the secret collections are shocking," said Akinsha. "In just one of the collections in the Hermitage -- the Krebs collection -- there are 78 paintings, including four Van Goghs, four Monets, 10 Renoirs, five C?zannes, two Manets, one Matisse, four Pissaros, one Picasso, and three Degas."


And according to Akinsha, the uncertainty over who legally owns the paintings has the art world in a frenzy of anticipation.


"Every art auction house in the world has tried to get the heirs to sign a contract," he said. "If the paintings are handed over, it could explode the market. Can you imagine the effect of four Van Goghs on sale at one time?"


Called "trophy art," the paintings were taken from Germany at the end of World War II. The art became part of the "special reserves," the existence of which was a closely guarded state secret. So secret were they that Pyotrovsky, whose father headed the Hermitage for 26 years, said he did not know of the existence of the collection until he became deputy director of the museum in 1991.


"Of course, there were people who knew," he said. "The paintings had to be maintained, and they are kept under the same conditions as the rest of the Hermitage collections. But no one else had access."


In the West, many of the paintings, including masterpieces by Van Gogh, C?zanne, Degas and Renoir, were believed to have been destroyed during the war.


"It was bad, it was a sin that these paintings were kept hidden all these years," said Pyotrovsky. "We have now decided to exhibit this part of our joint cultural heritage, plainly and openly."


That openness, however, remains far from complete. Pyotrovsky declined to state exactly how many art works would be displayed, saying only that it was "more than 70." And he coyly refused to name any of the paintings except for the two he had mentioned to The New York Times: "White House at Night" by Van Gogh, and "Place de la Concorde" by Degas."


We want to hold on to our information for a while," he laughed. "When we have prepared the catalog, we will make it public."


In the meantime, it is left for the art world to speculate. Akinsha and his colleague Grigory Kozlov have spent eight years researching Russia's secret troves of trophy art, and will publish a book on the topic in the spring.


The pair, working from once-secret government documents and historical records, have pieced together lists of Western art they believe are in Russia, and are now trying to find Russian cultural treasures that were stolen during the German occupation.


Pyotrovsky is dismissive of their efforts.


"They are working from the original KGB list that accompanied the artwork when it arrived from Germany," he said. "We do not have all of that art. The rest is just guesswork."


If so, it is guesswork with some basis. Kozlov worked in Moscow's Pushkin Museum, and had access to secret files and records. After he and Akinsha published an article on trophy art in New York's ARTnews magazine in 1991, Kozlov was fired from the museum staff.


"He stole material and made it public," sniffed Pyotrovsky. "Is that any way to make a living?"


The question of ownership of trophy art is also politically sensitive. A Russian-German commission has been established to deal with the question, but emotions run high on both sides.


"It is the last really serious issue left from the war," said one German official.


"Why should we give anything back?" fumed Vladimir Teteryatnikov, an art expert who advises the Duma on restitution issues. "Germany was the aggressor. They capitulated unconditionally. Why do we have to make any restitution? Those paintings are as much a part of our culture as the Kremlin."


Russian art experts cite the grave damage inflicted on Russian cultural sites during the war, including the deliberate destruction of Peterhof, Peter the Great's lavish palace on the Gulf of Finland, and the disappearance of Peter's fabulous Amber Room, which is believed to be buried somewhere in Germany. The artwork taken, they argue, was minor compensation for Russian losses.


Pyotrovsky seems to agree, up to a point. "It was a sin to hide the paintings," he said. "It was not a sin to take them." Pyotrovsky is the Russian head of the restitution commission, and he said the decision to go public had been made jointly by the German and Russian sides.


"But the legal status of the paintings is still an issue," he added.


And quite an explosive one. Most of the paintings are from private collections, meaning that the collectors' heirs could file claims against Russia for ownership.


Some of the better-known pieces that Akinsha and Kozlov believe to be in the Hermitage are, in addition to those mentioned above, "Portrait of Mademoiselle Lemonnier" and "Two Women in Black" by Manet, "The Boudoir" by Degas, "Man on a Stair" and "Woman on a Stair," both by Renoir, and "View of Mount St. Victoire" by C?zanne.