A Russian billionaire who paid at least $40 million to stop a collection of art being sold abroad said on Tuesday his decision to donate the artworks to the Russian government was 'irreversible'.

Metals magnate and co-owner of Britain's Arsenal soccer club, Alisher Usmanov, stepped in at the last minute to buy the collection, which the widow of Russian cellist Mstislav Rostropovich was selling at auction in London.

Firmly and irreversibly, it will belong to the state, state-owned Vesti-24 television showed Usmanov as saying. In this case I have no sense of being the owner. I think we will find some way to accommodate ... this (art) in our motherland.

Usmanov, who is worth an estimated $5.5 billion, paid substantially higher than the 20 million pound ($40 million) price tag for the collection of paintings, porcelain figures, and other items, Sotheby's auction house said.

Russia's billionaire tycoons, known as oligarchs, are widely resented at home, and President Vladimir Putin has encouraged prosecutors to examine whether they amassed their fortunes legally.

In recent years many tycoons have turned philanthropists, sponsoring Kremlin-backed projects or giving to charitable causes.

Red and White Holdings, an investment vehicle co-owned by Usmanov, said on Tuesday it had increased its stake in Arsenal Holdings Plc to 21 percent, making it the second-largest shareholder.