Yet the Uralkali affair stands out for illustrating with rare clarity the willingness of the authorities to use whatever means necessary to obtain these assets, including subjecting companies to questionable investigations that they have little chance of resisting, financial analysts here say.

At the forefront of these efforts is Mr. Sechin, 48, a deputy prime minister who has been a Putin confidant since the two served in the St. Petersburg city government in the early 1990s. Mr. Sechin almost never gives interviews or speaks publicly, but he is believed to spearhead the use of the secret services and other government arms to capture companies.

“He is the state’s main raider,” said Olga Kryshtanovskaya, a prominent Kremlin expert at the Center for the Study of Elites in Moscow. “He organizes these raider seizures, sometimes to the benefit of the state, or sometimes to the benefit of companies that are friendly to him.”

Mr. Sechin’s role in the Uralkali inquiry immediately caused analysts and investors to presume that the company was in peril. Uralkali’s stock, once highly prized by fund managers, has plunged more than 60 percent since the inquiry began, far more than the broader Russian stock market.

That has caused steep losses for Mr. Rybolovlev, 42, a former medical student who is known as Russia’s fertilizer king because of his dominance of the business of mining potash, a principal fertilizer component. Last June, when Uralkali was soaring, the otherwise low-key Mr. Rybolovlev attracted attention by buying Donald J. Trump’s mansion in Palm Beach, Fla., for $95 million.

The Kremlin has not said when there will be a decision on Uralkali, and the company is hoping to negotiate a settlement that would include a fine of a few hundred million dollars. Analysts emphasized that there was still a chance that Mr. Sechin might pull back after seeing the stock market react so hostilely to the inquiry.

Developments in the overall economy might also give the Kremlin pause. A growing recognition of its outsize influence over business appears to have helped sour the investment climate here, and suggests in part why the Russian stock market has been among the worst performers in the world this year.