Mr Berezovsky says he has been victimised

Mr Berezovsky was briefly held by the British authorities in April, in response to Moscow's request for his extradition to face charges of massive fraud.

He has been investigated over a series of contentious investments, most recently over accusations that he bilked a Russian regional government of billions of dollars owed by his car dealership empire.

Mr Berezovsky, who still claims to operate an empire worth billions of dollars both inside and outside Russia, says he is being victimised for his political beliefs.

He is one of the main backers of a fledgling liberal movement in Russia, which stands in opposition to nationalist President Vladimir Putin.

Ups and downs

The news may be controversial in the UK, since Mr Berezovsky is blamed by some for many of Russia's post-communist problems.

Like other flamboyant Russian tycoons, he profited from the rapid and chaotic privatisation process in the early 1990s, building up an empire encompassing media, banks, cars, energy and a stake in national airline Aeroflot.

He was a close ally of Boris Yeltsin, who was president during the most of the 1990s.

Under Mr Yeltsin's patronage, Mr Berezovsky became the leading member of the cabal of politically-involved business leaders known as oligarchs.

Many critics argue that the oligarchs retarded Russia's economic progress, by effectively pillaging state assets and spiriting billions of dollars overseas.

Wholesome role

Mr Berezovsky, meanwhile, has always defended his business record.

Oligarchs, he says, were the necessary catalyst for economic change in Russia, helping to create a vigorous entrepreneurial culture.

He says Mr Putin - a more authoritarian figure than his predecessor - has reined in capitalism, and stamped on liberal values.

Mr Berezovsky's efforts to build a credible opposition party have soured his relations with the Kremlin, which has turned the spotlight on his business dealings in an effort - he says - to discredit him.