SOFIA — A self-described Bulgarian looter has ignited an international controversy by admitting that he dug up an ancient treasure – a set of rare 12th-century silver dishes – and accusing Christie’s of trying to resell one of the dishes in London for far more than he ever got for it.

The case has developed into Bulgaria’s first high-profile effort to recover allegedly plundered antiquities, with prosecutors seeking the return of not just the dish that Christie’s was trying to sell, but also nine dishes that Sofia maintains are from the same set and now in the possession of three Greek museums.

Bulgaria contends that the rare Byzantine-era silver dishes were smuggled out of the country after being illegally excavated near the central town of Pazardjik in December 2000.

The case came to light last November when Naiden Blagnev, effectively incriminating himself, told the authorities that a dish being offered by Christie’s was part of a set of 13 that he had personally dug up six years earlier.

Blagnev, 36, said during an interview that he had contacted the authorities after seeing a picture of the Christie’s dish – with an estimated worth of £300,000 to £500,000, or $600,000 to $1 million – on the front page of a Bulgarian newspaper. He said he had been stunned by the Christie’s price for a single dish – as much as 60 times the amount he had received for the whole set.

“I wanted the truth to come out,” Blagnev said.

Upon hearing Blagnev’s story, Bulgarian prosecutors made an urgent official request to Britain to stop the auction. The central criminal court in London initially upheld the request. But later, citing lack of evidence, it ruled that the sale could go ahead. The dish failed to find a buyer, however, most likely because of media attention surrounding the case, and the piece was returned to its owner.

In addition to the Christie’s dish, Bulgaria claims that another nine dishes, on display in three Greek museums since October 2003, were part of the same set. The collection was bought jointly by two Athens museums – the Byzantine and Christian Museum and the Benaki – and the Museum of Byzantine Culture in Thessaloniki.

Bulgarian prosecutors are preparing a request for information from Greece. If that case reaches a courtroom, it will be the first known instance in which official Greek institutions have been accused of violating the import and provenance standards that Greece often accuses other countries of breaching.

Bulgaria, located on the territory of seven ancient civilizations, is one of the biggest source countries for illicitly exported antiquities in Europe, experts say.

“At the present time, Bulgaria is probably a bigger supplier than Italy and Greece,” said Neil Brodie, research director of the Illicit Antiquities Research Center in Cambridge, England.

Desperate poverty drives large numbers of Bulgarians to loot these ancient sites, and state controls are ineffective in halting the plunder. Corruption, weak law enforcement and the uneasy transition to a market economy after decades of communism have hindered Bulgaria from combating the trade in illicit antiquities.

The Bulgarian authorities are hoping that the case of the silver dishes will change the situation.

The prosecutor general, Boris Velchev, who took office in February 2006, has said that he will make prosecuting crimes against Bulgaria’s cultural heritage a priority.

“Until now the state has been inactive,” said Ivanka Kotorova, who is on a new team of prosecutors fighting crimes against cultural heritage. “This case will be a signal toward private buyers and museums to pay more attention to the origins of the objects they acquire, because they risk damaging their image and authority in the eyes of the world.”

The effort to recover the silver dishes is the new team’s first case.

According to a 2003 article on the new Greek acquisitions in a Benaki Museum publication, “the nine dishes were inherited by the present owner from his father, who acquired them in 1937 for £15,000 from A. Barry, an Englishman, who had been an exporter of currants in Smyrna until 1922 when he settled in Patras.”

“The provenance of the dishes is not known with certainty,” the article added, “but according to undocumented information from the original owner, they were discovered accidentally” outside Tatar Parardjik “in modern Bulgaria.”

Anna Ballian, curator of the Benaki’s Islamic and post-Byzantine collections, said that she had investigated the origin of the dishes and that this account of their provenance story checked out. But she would not name the London-based dealer who sold them to the museum.

In Britain, the owner of the Christie’s dish was listed in the catalog as “the Trustees of the Stanford Place collection.” This turned out to be Sir Claude Hankes-Drielsma, a prominent British business executive and patron of the British Museum who also served as an adviser in Iraq after the fall of Saddam Hussein and headed the Iraqi Governing Council’s fraud investigation into the United Nations-administered oil-for-food program.

Hankes’s lawyer, Ludovic de Walden, told the London court in November that it was “abundantly clear” that his client’s dish and the one sought by Bulgaria were two different objects. De Walden produced an invoice, dated July 7, 1998, showing that Hankes had bought a 12th-century silver dish for £200,000 from Sam Fogg, a well-known London dealer.

Fogg told the International Herald Tribune that he had sold the dish on behalf of another London dealer, whom he declined to name. He said there was evidence that the dish was in circulation before 2000, when the Bulgarian prosecutors say it was dug up, although he did not provide this proof.

“What the Bulgarians are claiming can’t possibly be true,” Fogg insisted.

But the Bulgarian prosecutors are convinced that Blagnev’s account is accurate because of an earlier court case, in 2001. In that case, Blagnev and his associates gave detailed descriptions of dishes they had looted that match the descriptions of many of the silver dishes now in dispute.

The testimony was given when Blagnev was on trial for extortion after assaulting and threatening to kill Marin Velkov, an antiques dealer who bought the set of 13 dishes from Blagnev for 30,000 Deutsche marks, or about $17,000 at the time.

Blagnev maintains that Velkov paid him in fake bank notes and that he was trying to get the dishes back. He was convicted of attempted extortion and served a year under house arrest.

There are also doubts among archaeologists of whether the dishes’ sudden “appearance on the scene,” as the Benaki publication put it, would have been possible if the antiquities had not been looted recently.

Such Byzantine-era vessels rarely survived because the silver was melted down to make other objects, said Margarita Vaklinova, a Byzantine expert at the Bulgarian Archaeological Institute and Museum in Sofia. Vaklinova estimates that there are only 30 or so comparable Middle Byzantine dishes in the world.

The idea that such an important collection could have remained unknown for so long is “absurd,” Vaklinova said.

“For the last 100 years, not a single publication appeared about these dishes,” she said, adding that the museum bought the collection “and looked for a myth.”

Ballian, of the Benaki, said she did not know where the dishes had been previously, but added: “It is not at all rare to find pieces buried in a private collection.”

So where have the dishes been all these years?

“If I knew all that,” Ballian said, “I would be Sherlock Holmes.”