A Russian tycoon, who has urged the West to help end Moscow's "insane war" in Ukraine, said Tuesday he had been punished by the Kremlin for his stance.

In an emotional post on Instagram in April, Oleg Tinkov, one of Russia's best-known self-made tycoons, said that "90 percent of Russians" were against the Kremlin's "massacre" in Ukraine.

Later that month, Tinkov sold his 35-percent stake in the holding he founded to a company controlled by Kremlin-friendly billionaire Vladimir Potanin. The TCS Group Holding owns Tinkoff Bank, one of Russia's largest lenders.

In a new post on Instagram on Tuesday, Tinkov, 54, said he had sold his stake for "kopecks", expressing gratitude to Potanin for rescuing him from "this looming hell."

"I've lost everything but I have not lost my soul," he said, adding he had also received threats.

In an interview with The New York Times published on Sunday, Tinkov said he had been forced to sell the stake at three percent of what he considered to be its real value. "I couldn't negotiate," he said, adding that friends, citing security service contacts, had told him that he could be in danger.

In recent years, Tinkov has been undergoing treatment for leukemia in the West.

"Threats to me personally, a person who is battling a devastating blood cancer, leukemia, the desire to punish me just for my opinion, my honest opinion, speaks of the final dehumanization of the regime," Tinkov said on Instagram.

"God bless you, inhabitants of the Kremlin and Lubyanka," he said, referring to the presidential administration and the headquarters of the FSB security service.

He said that a majority of Russian businesspeople were afraid to speak out.

"I don't know how much I have left to live, but I definitely don't want to die with these billions" and be a "coward".

He said he no longer had any business interests in Russia and was cutting his ties to the country.

"Farewell Tinkoff Bank, farewell Russia," he said.

"Ukraine will win because good always wins over evil, we were taught that at school!"