Jailed former oil tycoon Mikhail Khodorkovsky released a brief statement on Thursday in response to the recent death of self-exiled tycoon Boris Berezovsky.
In the statement, posted on Khodorkovsky's official website, the former Yukos CEO says that while he and Berezovsky were never friends, "we knew each other for more than 20 years."
"That's a long time," he said.
"It's hard to hear that Boris is gone forever. He loved life in all its manifestations, he made mistakes, he sinned, then repented and sinned again. I was angry at him a lot, and now he's gone, and it hurts me."
Berezovsky was found dead in his home in England last Saturday. A medical examination carried out by local police concluded that the cause of death was "consistent with hanging" but further tests are still being conducted and are expected to take several weeks.
Berezovsky and Khodorkovsky were both widely seen as embodiments of the wild 1990s, when the two businessmen made their respective fortunes and gained oligarch status.
They both later also openly criticized President Vladimir Putin.
Berezovsky openly slammed Putin on several occasions, once appearing before reporters wearing a Putin mask and carrying a poster reading, "I gave you life, so I will also be the one who calms you down."
Khodorkovsky, who was convicted of of tax evasion, fraud and money laundering in a case that many say was politically motivated, has been equally outspoken in his criticism of Putin, accusing him of resorting to political repression and pushing Russia back into an era of economic stagnation comparable to that seen under Soviet leader Leonid Brezhnev.