Greece's prime minister has expressed outrage over the British Museum's loan of one of the Parthenon sculptures to Russia's Hermitage Museum.
The loan is the first time in 200 years that any of the sculptures, also known as the Elgin Marbles and whose return Athens has long sought, has left Britain.
Prime Minister Antonis Samaras said the decision "provokes the Greek people".
He added "the Parthenon and its sculptures were the subject of looting."
The sculptures, which adorned the Parthenon temple atop the Acropolis for more than 2,000 years, are at the heart of one of the world's most famous cultural disputes.
They were removed in the early 19th century by Britain's ambassador to the Ottoman Empire when Greece was under Ottoman occupation.
The British Museum says the marbles will not be sent back to Greece.