France has secretly returned four solid gold antiquities looted from China and bought by billionaire luxury tycoon François Pinault, as Beijing steps up efforts to repatriate pillaged art, according to a report by the Daily Telegraph this Monday.

The four gold heads of birds of prey, worth €1 million, were looted in 1992 from the tomb of a noble of the Zhou dynasty in Gansu province. According to China, they were part of a wave of thefts in the mid-1990s by farmers from sites in the western state of the Qin, which founded the first imperial dynasty.

The report also said that the return proved a diplomatic nightmare since gifts to French museums are in theory irrevocable.

At least 10 million Chinese artifacts were illegally transported overseas in the past centuries.