1109 GMT October 23, 2019
The move was billed by Italian officials as "the first case of such close cooperation between Italy and a private auction house".
According to sky.com, it is part of Rome's long-standing efforts to repatriate antiquities it says were illegally obtained and trafficked on the art market.
The items feature a marble fragment from a sarcophagus in Rome's Catacombs of St Callixtus, a piece with a market value of £50,000.
Other works include an Etruscan terracotta mask that dates to between the 6th and the 5th century BC, ancient Greek plates and vases, and an ancient Roman capitol.
Italy said the items were looted between the 1960s and 1980s and illegally trafficked. Christie's said the works had been ‘acquired in the past in good faith’ but "were more recently identified as not having the required, verifiable title, export or provenance details needed to proceed with a sale".
It stressed that the items, put on display during a ceremony at the Italian Embassy in London that drew Rome's culture minister Alberto Bonisoli, had been returned voluntarily.
"Our primary goal is to return these objects and to raise awareness of how vital it is to have access to all information to continue to ensure only legitimate works are offered to the market," said Stephen Brooks, deputy chief executive officer at Christie's.
"Our processes of due diligence make full use of current, available research and we continue to work closely with organizations, authorities and art loss databases to ensure we have verifiable title and provenance."
Italy's vast cultural heritage, sometimes lying unguarded, has fallen prey to illegal traffickers for decades. Rome's art theft police have a database that catalogues some 1.2 million stolen objects.
It is the largest such archive, Italian art officials say.
For more than a decade now, Rome has stepped up efforts to obtain art it says was excavated by grave diggers and smuggled out of the country, including works kept in museums around the world.
Over the years, it has struck deals with museums for the return of antiquities, including the Metropolitan Museum in New York and the Getty Museum in Los Angeles.
In December, Italy's highest appeals court ruled that a bronze statue from two millennia ago, called Victorious Youth, should be repatriated. Getty has disputed the ruling, saying the statue had been found in international waters.