Exiled Russian oligarch Boris Berezovsky -- a onetime Kremlin insider who became one of President Vladimir Putin's fiercest critics -- has died at the age of 67.
Berezovsky was found dead at his home outside London, his family announced. The cause of death is unclear.
One of the key political figures in Russia in the 1990s during the presidency of Boris Yeltsin, Berezovsky was instrumental in engineering Putin's rise to power. He later fell out with the new Kremlin leader and went into exile in Great Britain in late 2000.
Berezovsky was the leading figure among the Yeltsin-era "oligarchs," a group of politically connected businessmen who profited mightily from the wave of privatizations that followed the breakup of the Soviet Union and controlled most of Russia's energy companies, media outlets, and its banking sector in the 1990s.
He was also the informal leader of the so-called "Family," a group of Kremlin insiders who were widely believed to wield enormous influence over Kremlin policy as the aging and ailing Yeltsin became an increasingly ineffectual ruler.
In exile, he became one of Putin's fiercest antagonists, helping bankroll opposition to him and mocking attempts by the Kremlin to have him extradited.
In a controversial 2007 interview with the British daily "The Guardian," Berezovsky called for Putin's forceful overthrow.
"We need to use force to change this regime because, first of all, this regime is anticonstitutional. It means that I call to use force to re-create a constitutional regime again,” Berezovsky said.
“It means I am for the constitution and Putin is against the constitution. And understanding that Putin created an authoritarian regime, I [submit] that there is no chance to change that through elections. The only way is to use power."
Berezovsky later clarified in an interview with RFE/RL that he meant Putin should be overthrown in a popular revolt similar to Georgia's Rose Revolution and Ukraine's Orange Revolution.
"What happened in Ukraine, what happened in Georgia, are typical examples -- in my understanding -- of a forceful seizure of power when the street, the square, put pressure on the rulers -- forceful pressure on the rulers -- in order to change the regime," Berezovsky said.
Berezovsky was born on January 23, 1946, in Moscow.
He studied forestry and later applied mathematics and spent nearly two decades in academia before taking advantage of Mikhail Gorbachev's economic reforms and the chaos of the post-Soviet period to make a fortune in business.
In 1989 he founded an auto dealership, Logovaz, and made a small fortune importing Mercedes cars into Russia. He also set himself up as a middleman distributing cars made by the Russian auto giant AvtoVAZ.
He used that wealth and the political connections he made to gain control of key sectors of the Russian economy in rigged privatizations. By the mid-1990s, his assets spanned the energy, media, and airline industries.
In 1994, he gained de facto control of the country's top television station, then called Russian Public Television (ORT), and appointed the popular anchor Vladislav Listev as its CEO. Months later, in March 1995, Listev was assassinated. He had also reportedly had a falling out with Berezovsky.
In the controversial 1995-97 "loans-for-shares" auctions in which leading businessmen acquired stakes in top state-owned enterprises at knock-down prices, he and Roman Abramovich gained control of Sibneft, Russia's sixth-largest oil company.
He also choreographed a management reshuffle at the state airline Aeroflot, placing key associates in top positions.
Berezovsky gained access to Yeltsin's inner circle when he arranged for the publication of his memoirs and befriended the Kremlin leader's ghostwriter, Valentin Yumashev. He also befriended the president's daughter, Tatyana Dyachenko.
Berezovsky and the other oligarchs pooled their resources and media assets to help ensure that Yeltsin would be reelected in 1996.
After Yeltsin's elections, Berezovsky boasted in an interview with Britain's "Financial Times" that he and six other financiers controlled roughly half the economy and the lion's share of the national media.
He briefly became secretary of Yeltsin's Security Council and helped to broker the peace deal that ended the first Chechen war.
In 1998, political analyst Sergei Markov described Berezovsky as "a modern-day Rasputin, secretively manipulating the president and his entourage."
As Yeltsin's second term wound down and his health deteriorated in the late 1990s, Berezovsky and other Kremlin insiders began seeking a suitable successor who would guarantee their continued wealth and access to Russian leaders.
They eventually settled on Putin, whom Yeltsin appointed prime minister and named as his successor in August 1999.
Aided by a media campaign spearheaded by ORT, Putin's popularity soared. He launched the second Chechen war in late 1999 following a series of suspicious apartment bombings in Moscow that were never explained but which the authorities blamed on Chechen rebels.
After Yeltsin unexpectedly resigned on New Year's Eve 1999, six months before his term expired, Putin became acting president. He was elected president in March 2000.
But Putin turned out to be far from the pliant figure Yeltsin was, and he quickly turned on Berezovsky and moved to neutralize the influence of the oligarchs and other members of Yeltsin's court.
Berezovsky fled to Britain in late 2000 and was granted political asylum in 2003.
Russian authorities opened a series of criminal cases against Berezovsky and tried repeatedly -- and unsuccessfully -- to have him extradited.
Berezovsky seemed to delight in mocking these attempts. He famously came out of one extradition hearing in 2003 wearing a Putin mask, telling reporters: "Call me Vladimir Putin."
He became the most high-profile figure in a group of anti-Putin emigres in London that included Chechen rebel envoy Akhmed Zakayev and former security agent Aleksandr Litvinenko, whose 2006 poisoning death Berezovsky blamed on the Kremlin.
He warned in 2007 that Putin's Russia was a danger to the West.
"I think the sooner the West recognizes that Russia is not an ally, that Russia is not a partner -- I mean Putin's Russia -- this will help the West more quickly find the tools to protect themselves," Berezovsky said.
Meanwhile, Berezovsky's wealth began to dry up. In 2012, he lost a $5.1 billion lawsuit against Abramovich in a dispute over shares in Sibneft. He accused Abramovich of blackmail and breach of contract.
The lawsuit cost Berezovsky hundreds of millions of dollars in legal fees and left his reputation in tatters.
In her ruling against him, Judge Elizabeth Gloster called Berezovsky an “unimpressive and inherently unreliable witness” and at times a dishonest one. She also ordered him to pay $53 million of Abramovich's legal costs.
His financial difficulties were also highlighted recently when his former mistress, Yelena Gorbunova, claimed Berezovsky owed her $8 million in compensation for the sale of their $40 million residence in Surrey, outside London.
According to news reports, in the months prior to his death, Berezovsky closed his London office and was selling his assets, which included mansions, a 1927 vintage Rolls Royce, and the famous Andy Warhol print "Red Lenin."
In an open letter posted on his Facebook account in February 2012, Berezovsky asked Russians for forgiveness for his transgressions. He specifically apologized for engineering Putin's rise to power and not seeing in him "the future greedy tyrant and usurper who killed liberty and stopped Russia's development."
But Kremlin spokesman Dmitry Peskov told Russian state television that, shortly before his death, Berezovsky had asked Putin for forgiveness and sought permission to return to Russia.
"Some time ago, maybe a couple of months back, Berezovsky sent Putin a letter that he personally wrote in which he said that he realizes that he had committed a great number of mistakes," Peskov said.