France has promised to return seven paintings taken from their Jewish owners during the second world war, part of efforts to give back hundreds of looted art that hangs in the Louvre and other museums.

The works were stolen or sold under duress up to seven decades ago as their owners fled Nazi-occupied Europe. All seven were destined for display in the art gallery Adolf Hitler planned to build in his birthplace of Linz, Austria, according to a catalogue for the proposed museum.

At the end of the war, with Hitler dead and European cities rebuilding, the paintings were unclaimed, and many thousands thought to have been French-owned were later displayed in the country's top museums.

The move to return the paintings ends years of struggle for the owners' families, whose claims were validated by the French government last year.

"This is incredibly rare. It's the largest number of paintings we've been able to give back to Jewish families in over a decade," said Bruno Saunier of the National Museums Agency. Many of the 100,000 possessions looted, stolen or appropriated between 1940-44 in France have been returned to Jewish families, but Saunier said the country had increased its efforts in the past five years to locate the rightful owners of what the French government says are some 2,000 artworks in state institutions. Archiving errors and the challenge of identifying the paintings have made it slow process.

Six of the paintings – among them works by Alessandro Longhi, Sebastiano Ricci and Gaspare Diziani – were owned by Richard Neumann, an Austrian Jew whose ticket out of France was his art collection, which he sold off at a fraction of its value.

It is not clear to whom Neumann sold them, and the route they took to show up in French museums is unclear. They found homes at the Louvre, the Museum of Modern Art of Saint-Etienne, the Agen Fine Arts Museum and the Tours Fine Art Museum.

Neumann's grandson, Tom Selldorff, was a young boy in 1930s Vienna when he last saw his grandfather's collection. At 82, the US resident is going to get them back and wants to pass a piece of his Austrian grandfather's heritage down to his children.

"Tom is 82 years old ... So time is important; they need to act quickly," said Muriel de Bastier, arts chief of the Spoliation Victim's Compensation Commission, a French government body that helps families retrieve stolen work.

The other painting, The Halt by Dutch painter Pieter Jansz Van Asch, was stolen by the Gestapo in Prague in 1939 from a Jewish banker, Josef Wiener, who was later deported and died in the Theresienstadt concentration camp.

After the war, the painting was confused with a work owned by a Frenchman and erroneously sent to Paris, so Wiener's widow's efforts to locate the painting in Germany were fruitless.

For years it hung in the Louvre, until the family tracked it down online in the mid-2000s. After problems identifying the painting were resolved, the thenFrench prime minister François Fillon gave the family the green light to give it back last year.

Other Jewish-owned property was "legally" appropriated by the state. Some 100,000 houses were seized and sold to non-Jews between 1940 and 1944, as the Vichy government copied the Nazi's anti-Semitic policy of "Aryanisation" – of displacing Jews from society. The French state then pocketed the money.

A national exhibit at Paris's Shoah Memorial confronts the issue for the first time, tracing the 1941 creation of a commission that enforced the seizures, often with the help of volunteers called "administrators". They exercised full rights over the property of Jewish families.

All around the country, billboards, posters and classified ads in newspapers appeared, calling on the public to buy the stolen property.

The exhibit features one that reads: "For sale: beautiful bourgeois home", or another in bold writing: "Sale of Jewish property ... belonging to (an) Israelite".

The exhibit's curator, Tal Bruttmann, said this was the only time in history where the state called on the whole nation to take part in antisemitism. "It's a crucial story that has not been told before," he said. The exhibtition runs until 21 September.