The Czartoryski collection of about 86,000 pieces, based in the city of Krakow, includes da Vinci's Lady with an Ermine and works by Rembrandt.

It was sold for €100m ($105m; £85m) despite being estimated at about €2bn.

The management board of the Czartoryski Foundation resigned in protest at the bargain price.

The board says it was not consulted about the sale, which was negotiated between Poland's culture Ministry and the head of the family which owns the collection, Adam Karol Czartoryski.

Mr Czartoryski said he was supporting the Polish nation by accepting the offer, effectively making a large donation to the state.

He said he "felt like making a donation" and that it was his choice to make.

In addition to the artworks, the Czartoryski collection includes about 250,000 manuscripts and books. All are now the property of the Polish state.

Poland's culture ministry said negotiations for the collection had taken several months.

Lady with an Ermine, painted in 1490, is one of only four portraits of women by Da Vinci.

It shows Cecilia Gallerani, a young woman in the Milanese court who was mistress to Ludovico Sforza, the Duke of Milan.

His nickname at court was "the white ermine" - explaining the animal's presence in her arms.

It was stolen from Poland by Nazi forces during World War Two, but later repatriated and restored to its owners.

In 2014, new techniques revealed that the painting had been changed at least twice - with the eponymous animal only being added in a later version.

Other famous works in the acquired collection include Rembrandt's Landscape with the Good Samaritan and drawings by the French artist Pierre-Auguste Renoir.

Parts of the collection have been housed in the National Museum in Krakow for many years.

(BBC)