Beketov, who once had his car blown up, was beaten after calling for the resignation of the municipal government in the city of Khimki. Three of his fingers and a leg had to be amputated and he lived out his years using a wheelchair, The New York Times reported.
Police spent little effort trying to find his attackers, the newspaper said, despite witnesses' accounts and surveillance videos.
Yevgenia Chirikova, an environmental activist from Khimki, said Beketov never recovered physically from the attack.
"In essence, they killed him back then," she told the Times in a telephone interview. "He was just dying all these years. That's all."