Greece on May 23 urged Britain to return the Parthenon Marbles- often known as the Elgin Marbles- as one of the world’s greatest ancient sites the Acropolis re-opens after the coronavirus shutdown.

The ancient friezes, which include depictions of battles between mythical ancient Greeks and centaurs, were taken by British diplomat Lord Elgin in the early 19th century and are now on display at the British Museum in London.

Britain has always refused to return them, arguing that they were taken with the permission of local Ottoman rulers at the time.

"The reopening of the archaeological sites with the Acropolis among them, is an occasion for the international (groups) supporting the return of the Parthenon Marbles to reaffirm their constant demand as well as that of the Greek government for the definitive return of the marbles to their homeland," Culture Minister Lina Mendoni said in a statement.

Greece reopened the Acropolis in Athens and all open-air archaeological sites last week under tight conditions after a two-month closure due to the coronavirus pandemic.

The International Association for the Reunification of the Parthenon Sculptures- formed in 2005 in Athens and which comprises various national groups- last week sent a letter to the Greek Ministry of Culture proposing a renewed, coordinated campaign to put pressure on the British Museum.

Mendoni said Saturday that the Marbles were "loot" and Greece would never recognize the British Museum’s claim to the friezes.

Greece has been campaigning for three decades for their return, arguing that the Ottoman empire was an occupying force and any permission granted during its time is not valid.

Athens has considered suing Britain over the issue but more recently has taken a more diplomatic route, asking the U.N.’s cultural agency UNESCO to mediate- an offer rejected by the British Museum.

Prime Minister Kyriakos Mitsotakis, elected in July, has made an official request for the loan of the marbles to mark the 200th-anniversary celebrations of Greek independence in 2021.

The British Museum has said it would examine any request from Greece to borrow exhibits.