Boris Berezovsky, the exiled Russian oligarch, has been found dead at his mansion in Surrey, England. He was 67.
His death was confirmed in a Facebook post by his son-in-law, Egor Schuppe.
The circumstances of his death remain unclear, with further details yet to be released, though initial reports suggested he had committed suicide. The coroner was said to have attended the Berezovsky home.
According to Schuppe, Berezovsky had been depressed, had failed to return calls, seldom left his residence and in his final days spent most of his time indoors.
Damian Kudriavtsev, the former CEO of Kommersant Publishing House, issued a Twitter post saying Berezhovsky died at 11am in London, but that there were no signs of a violent death.
Aleksandr Dobrovinksy, head of Moscow-based Alexander Dobrovinsky & Partners law firm, said Berezovsky had taken his own life.
"Just got a call from London. Boris Berezovsky committed suicide. He was a difficult man. A move of disparity? Impossible to live poor? A strike of blows? I am afraid no one will get to know now," Dobrovinksy said.
Last year, Berezovsky lost a High Court case in London against Chelsea FC owner Roman Abramovich over the ownership of Sibneft, where Berezovsky had sought more than £3 billion in damages. The row centred around murky dealings in the world of Russian business following the collapse of the Soviet Union, when the state's vast assets were auctioned off at huge discounts by then president Boris Yeltsin.
Berezovsky had been planning to auction a portrait of Communist leader Vladimir Lenin by Andy Warhol, to raise money to pay off creditors and settle legal fees, it was reported last week. The 1987 portrait was valued at between $45,000 and $75,000, by auction house Christies.
Berezovsky had been on Russia's wanted list since 2001 on charges of fraud, money-laundering and an illegitimate bid to seize power. The tycoon, who was born 1946, fled Russia in the late 1990s amid a money-laundering scandal surrounding the Russian state airline Aeroflot.
In 2007, a Russian court found him guilty in absentia of embezzling 215 billion roubles in Aeroflot funds, and he was sentenced him to six years in prison. In total, he was sentenced to 19 years' imprisonment by Russian courts on various charges.
Berezovsky said the cases against him were concocted by Russian President Vladimir Putin. He was granted political asylum in Britain in 2003.
He made his fortune in Russia in the 1990s, gaining control over state assets including the country's main television channel, Channel One. Berezovsky commanded immense power during the last years of Yeltsin's presidency, when he was deputy secretary of Russia's security council.
After Putin came to power in March 2000, Berezovsky went into opposition and resigned from the Duma.
In 1997 Forbes magazine estimated Berezovsky's wealth at US$3 billion. After his flight from Russia, many of his assets were confiscated by the state.