US museums have come under fire over the way they acquire antiquities after Greece, Italy and Peru have demanded the return of ancient pieces from American institutions.

European museums have usually been the ones needing to answer over their acquisitions of artifacts collected during colonial days, but American institutions have faced demands for the return of allegedly looted antiquities.

To improve the transparency of acquisitions, the Association of Art Museum Directors (AAMD) released new guidelines last month on loans of antiquities and ancient art.