A long-running dispute over a collection of roughly 1,800 paintings attributed to Russian modernist masters has escalated after a litigation funder said it may have been misled about the works’ authenticity. The development has added a new layer of tension to a case already entangled in competing ownership claims, criminal investigations, and multimillion-dollar lawsuits across several countries.

The controversy centers on the late Palestinian collector Uthman Khatib, his son Castro Ben Leon Lawrence Jayyusi, and their Prague-based litigation funder, LitFin. Beginning in 2023, LitFin backed lawsuits brought by the Khatibs against Israeli-Russian businessman Mozes Frisch, whom they accuse of stealing all 1,800 paintings. They are seeking the return of the paintings or damages of approximately $323 million, the collection’s purported fair market value. The collection includes paintings attributed to El Lissitzky, Natalia Goncharova, and Kasimir Malevich.

But the paintings themselves have a long and checkered history. Their original owner, the late Israeli art dealer Itzhak Zarug, was convicted in 2018 in Germany of selling forgeries. As part of the investigation into Zarug, Germany’s Federal Police (BKA) seized the 1,800 artworks in 2014. The BKA previously told ARTnews that it believed all of the works were forgeries, citing improper storage conditions and what they described as implausible or opaque provenances supported by assessments from dubious art historians. All of the paintings seized in 2014 were registered with the Art Loss Register, the world’s largest database of lost and stolen art, in 2018. While the paintings were under confiscation in 2015, Zarug sold Khatib a 49 percent stake in the collection. But just months after German authorities returned nearly all of the seized paintings to Zarug in 2019, Frisch allegedly removed them from a German storage facility.

The Khatibs filed a lawsuit against Frisch in Frankfurt in 2023, accusing him of theft, a charge he has denied, maintaining that he is the lawful co-owner of the collection. He has based that claim on a private ownership agreement between him, Khatib, and Zarug in 2020 that purported to divide the collection. (Khatib and Zarug both died last year.)