Activists are demanding the return to Gabon of a rare 19th Century wooden mask sold in France for nearly $5m (£3.8m).
Nobody was expecting the pale mask with an elongated face and straggly beard to fetch even a tenth of the sum it was sold for.
Activists disrupted the auction in the southern French city of Montpellier, saying whoever bought the mask was receiving stolen goods.
The auctioneer insisted the sale was entirely legal.
The mask would have been worn by a member of the Ngil secret society, a group that travelled through villages dispensing justice and hunting down sorcerers.
The distinctive shape of the Ngil masks is believed to have played a huge influence on the work of famous European artists including Picasso and Modigliani.
Like many others in Africa, the Gabonese are demanding the return of precious artefacts stolen during colonial times.
A number of Western museums have started the process of returning precious antiquities stolen from Africa and other continents during colonial times.
