Alexander Perepilichny, 44, sought refuge in Britain three years ago and had been helping a Swiss investigation into a Russian money-laundering scheme by providing evidence against corrupt officials, his colleagues and media reports said.
He has also provided evidence against those linked to the 2009 death of anti-corruption lawyer Sergei Magnitsky, a case that caused an international outcry and prompted the United States to push for a bill cracking down on Russian corruption.
Perepilichny, a Russian citizen, collapsed and died abruptly outside his home on an upmarket estate in the English county of Surrey on Nov. 10, police said on Wednesday, the first time the case has come to light.
Perepilichny is the fourth person linked to the Magnitsky case to have died in strange circumstances.
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