LONDON -- Boris Berezovsky, a self-exiled and outspoken Russian tycoon who had a bitter falling out with Russian President Vladimir Putin, was found dead on Saturday in Ascot, a town 25 miles west of London. He was 67.
In recent years, the one-time Kremlin powerbroker-turned-thorn in Mr. Putin's side fended off verbal and legal attacks in cases that often bore political undertones -- and bit into his fortune.
The cause of Mr. Berezovsky's death was not immediately clear, and Thames Valley police said it was being treated as "unexplained."
Lawyer Alexander Dobrovinsky told Russian state TV that his client -- who had survived assassination attempts in the past -- lately had been in "a horrible, terrible" emotional state.
"All he had was debts," Mr. Dobrovinsky said. "He was practically destroyed. He was selling his paintings and other things."
A mathematician-turned-Mercedes dealer, Mr. Berezovsky amassed his wealth during Russia's chaotic privatization of state assets in the early 1990s following the collapse of the Soviet Union. In return for backing former Russian President Boris Yeltsin, he gained political clout and opportunities to buy state assets at knockdown prices, making a fortune in oil and automobiles.
He also played a key role in brokering the rise of Yeltsin's successor, Vladimir Putin, in 2000. But Mr. Berezovsky later fell out of favor with Mr. Putin, and eventually sought political asylum in the U.K. in the early 2000s to evade fraud charges he contended were politically motivated.
Mr. Berezovsky was one of several so-called Russian "oligarchs" to butt heads with Mr. Putin.
After coming into power, the Russian president effectively made a pact: the oligarchs could keep their money if they didn't challenge him politically. Those who refused often found themselves in dire circumstances. Some were imprisoned -- like the former Yukos Oil chief Mikhail Khodorkovsky -- while others, like Mr. Berezovsky, fled Russia.
The assets of these pariah businessmen, meanwhile, were acquired by state corporations or cooperative tycoons, often at bargain prices.
Over the years, Mr. Berezovsky accused Mr. Putin of leading Russia toward dictatorship and returning it to a Soviet-style system of state monopoly on the media.
In the U.K., Mr. Berezovsky allied himself with an array of other Kremlin critics. Among them was ex-KGB agent Alexander Litvinenko, who fled Russia with Mr. Berezovsky's help after accusing officials there of plotting to assassinate political opponents.
Litvinenko died on Nov. 26, 2006, after drinking tea laced with a lethal dose of the rare radioactive isotope polonium-210 in a London hotel. From his deathbed, Litvinenko accused the Kremlin of orchestrating his poisoning, and British police named former KGB agent Andrei Lugovoi as the prime suspect.
Both Mr. Lugovoi and the Kremlin denied the accusations, with the former instead claiming that Mr. Berezovsky -- whom Russia repeatedly sought to extradite on a wide variety of criminal charges -- engineered Litvinenko's death as a way of embarrassing the Kremlin and buttressing his refugee status.
Mr. Berezovsky, who considered Litvinenko a close friend, consistently denied the allegations. In 2010, he won a libel case against Kremlin-owned broadcaster All-Russian State Television and Radio Broadcasting, which aired a show in which it was suggested he was behind the former agent's poisoning.
Mr. Berezovsky, too, was the target of assassination attempts. In 1994, a car bomb injured him and killed his driver. He also said he briefly fled the U.K. in 2007 when British intelligence services told him his life was in danger.
More recently, Mr. Berezovsky has made headlines for costly legal battles that have dealt serious blows to his finances.
Last year, the Russian business magnate was ordered to pay 35 million pounds ($53.3 million) in legal costs to fellow Russian Roman Abramovich, the billionaire owner of Chelsea Football Club, after losing a multimillion-dollar legal battle against him.