Then, last month, Mr. Tinkov, the founder of one of Russia’s biggest banks, criticized the war in Ukraine in a post on Instagram. The next day, he said, President Vladimir V. Putin’s administration contacted his executives and threatened to nationalize his bank if it did not cut ties with him. Last week, he sold his 35 percent stake to a Russian mining billionaire in what he describes as a “desperate sale, a fire sale” that was forced on him by the Kremlin.

“I couldn’t discuss the price,” Mr. Tinkov said. “It was like a hostage — you take what you are offered. I couldn’t negotiate.”

Mr. Tinkov, 54, spoke to The New York Times by phone on Sunday, from a location he would not disclose, in his first interview since Mr. Putin invaded Ukraine. He said he had hired bodyguards after friends with contacts in the Russian security services told him he should fear for his life, and quipped that while he had survived leukemia, perhaps “the Kremlin will kill me.”