LONDON (AP) — The British Museum has loaned one of the Parthenon Marbles to Russia's Hermitage Museum — the first time in 200 years that any of the ancient sculptures has left Britain. The move outraged Greece, which has demanded that the marbles be permanently returned.

The marble sculpture of the river god Ilissos —a reclining male figure from the west pediment of the Parthenon — will be part of a major exhibition on Greek art being held as the Hermitage marks its 250th anniversary. The museum in St. Petersburg is Russia's most renowned.

The British Museum's trustees described the sculpture as a "stone ambassador of the Greek golden age," whose loan should continue despite the tensions between Britain and Russia over Ukraine. The loan runs from Dec. 6 to Jan. 18.

"The trustees have always believed that such loans must continue between museums in spite of political disagreements between governments," said British Museum director Neil MacGregor.

In Athens, Greek Prime Minister Antonis Samaras issued a sharply worded statement — replete with exclamation points — describing the British Museum's move as a provocation.

"Greeks identify with our history and culture!" he said. "Which cannot be sliced up, loaned or given away!"

The sculptures are at the heart of one of the world's most famous cultural heritage disputes.

The marbles decorated the Parthenon temple on the Acropolis for more than 2,000 years, but were removed at the beginning of the 19th century by Scottish nobleman Thomas Bruce, the 7th Earl of Elgin, when it was fashionable for the aristocracy to collect ancient art.

Athens says they were removed while Greece was under Turkish occupation. The British Museum has long rejected their return, arguing that in London the marbles can be seen by a global audience, free of charge.

Efforts to return the works were recently given a fresh boost by lawyer Amal Clooney, wife of actor George Clooney, who stepped in to back the Greek cause.

The chairman of the Marbles Reunited campaign, Liberal Democrat lawmaker Andrew George, criticized the trustees for snubbing the Greek request for the return of the sculptures and lending them instead "to a country which has backed rebels who kill British citizens."

"I sense that the British Museum's grip on the sculptures is weakening," he said.

The trip to the Hermitage marks the first time the sculptures had been requested for a loan to another country. The sculptures have never left the museum since being presented to the trustees by Parliament in 1816, with the exception of their evacuation for safekeeping in wartime.

The trustees have said they will consider any request for any part of the collection to be borrowed with the precondition "that the borrowing institution can guarantee its safe return."

The trustees said the loan to the Hermitage recognizes and celebrates "the parallel histories and common aims of two great museums."

"Both were founded on Enlightenment principles and both are united in working to take such principles forward through the 21st century," the museum said.

Britain's government played no role in the loan. Authorities note that the British Museum is independent of the government — a view it has often repeated as Greece sought to have the marbles returned.

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Elena Becatoros in Athens contributed to this report.