The museum says it will "vigorously defend its ownership of the statue"
A judge in Italy has ordered the Getty Museum in the US city of Los Angeles to return an ancient Greek bronze statue.
Prosecutors say the statue, of a young athlete crowned with an olive wreath, was smuggled out of Italy in the 1970s.
They say the museum failed to check the provenance of the statue when buying it for almost $4m (£2.5m) in 1977.
The museum says it bought the bronze, named the Statue of Victorious Youth, in good faith, and it would challenge what it called a "flawed" ruling.
More than 2,000 years old, it was found in the sea by Italian fisherman in 1964 off the eastern town of Fano, near Pesaro.
'Hidden by priest'
It is said to have been hidden by a priest, later leaving Italy in a shipment of medical supplies to Brazil.
It was eventually bought by an art consortium in 1971, which later sold it to the Getty Museum.
Also known as the Getty bronze, it is considered to be one of the greatest bronze statues to survive from ancient Greece.
In the ruling, Judge Lorena Mussoni ordered that the statue "be seized from the Getty Museum or wherever it may be at the moment".
Former Culture Minister Francesco Rutelli, who led Italy's efforts to recover the work, told the AFP news agency that the verdict was of "historic importance, ending the era of looting our archaeological heritage".
In a statement, the J Paul Getty Trust, one of the wealthiest art institutions in the US, said the court's order was "flawed both procedurally and substantively".
The trust said it would "vigorously defend its legal ownership of the statue".
Three years ago, and without admitting liability, the museum agreed to return 40 ancient artefacts in return for the long-term loan of other treasures.