The artworks are a Greek terracotta cup dating back to the 5th century BC and two ancient Roman sculptures from the 2nd century.

One of the marbles was stolen from an archaeological site. The other was taken from a private Italian collection. Both were sold by thieves to dealers who then sold them for millions of dollars to the museum, one of the world's wealthiest art foundations.

Stolen goods

The museum said recent investigations showed the Greek cup, the most important of the three artifacts, had been stolen from another archaeological site in Italy which is still being excavated.

Fragments were sold to the museum from 1983 onwards, a few at a time at an ever increasing price. This eventually aroused suspicions that the dealers were trying to pass off stolen goods.

The ceremonial cup - nearly a metre in diameter - is signed by the potter Euphronious and decorated with scenes from the Trojan War. It was brought from Greece by the Etruscans, the pre-Roman inhabitants of central Italy.

Another vase by Euphronious is currently in the Metropolitan Museum of New York.

Italian scholars say it was stolen from the same excavation site as the cup. But the museum's trustees have refused requests to return it.

Italy slams US museums

The Italian authorities have for years criticized wealthy museums and collectors, particularly in America, for buying stolen artworks.

They now hope the return of the three artifacts will mark the start of a better relationship between the antiquities departments of Mediterranean countries and foreign museums.

Marion True, the deputy director of the Getty Museum, said the trustees now only buy artworks whose origin can be clearly traced.

The foundation would not give a value for the three returned items.