Hollywood actor-director George Clooney has called for stolen artworks to be returned to their rightful owners, adding many works looted by the Nazis are still unaccounted for.

“There is a lot of art that is still missing,” Clooney said during a press conference on Saturday at Berlin’s Berlinale Film Festival, which marks the European launch of his new film The Monuments Men.

The film – directed, co-written and starring Clooney – is based on the true story of a special US military unit charged with tracking down and protecting art during the World War II.

“It’s a story that is going to keep coming up,” Clooney said.

The film also stars Cate Blanchett as a French art expert, Matt Damon as an art restorer and John Goodman as a sculptor and Bill Murray as an architect.

Blanchett’s character was based on Rose Valland, a woman who secretly kept records of the artworks stolen and shipped out of France by the Nazis at great personal risk.

In his comments, Clooney also backed Greece’s long-running campaign to retrieve antiquities looted by the Brits – notably the priceless Elgin Marbles currently on display in the British Museum.

“I think (Greece) has a good case to make,” said Clooney.

“It would be a very fair and nice thing to happen.”

Clooney is featured in The Monuments Men as Frank Stokes, a bespectacled art historian who leads a mission to shield Europe’s great works of art – not just from Hitler, but also from allied bombing and advancing Soviet forces.

Many of the works in question were earmarked for Hitler’s planned Fuehrer Museum and the private collections of top Nazis like Hermann Goering.

“For the first time the victors did not keep the spoils,” said Clooney.

“It is the kind film that I grew up with,” Clooney said, referencing other major war movies such as The Guns of Navarone and The Great Escape.

The Monuments Men is being screened at the Berlinale out of competition. It is Clooney’s fifth feature film as director.

The film’s release in Europe is particularly timely. It comes only months after the sensational find of more than 1,400 modern classics in a Munich apartment owned by the son of a prominent Nazi art dealer.