Billionaire Suleiman Kerimov asked the Federal Anti-Monopoly Service for permission to purchase Dmitry Rybolovlev's entire 63.2 percent stake in Uralkali, but a spokesman said it was an error and that Kerimov only wanted the 25 percent he ultimately bought.

On Monday, Uralkali announced that Rybolovlev had sold 53.2 percent of the potash maker to three firms: Kerimov's Kaliha Finance (25 percent), billionaire Alexander Nesis's Aerellia Investments and fellow billionaire Filaret Galchev's Becounioco Holdings. Uralkali said Tuesday that Rybolovlev kept 10 percent, while Galchev bought 15 percent and Nesis took 13.2 percent.

But on Tuesday evening, the anti-monopoly service said all three companies were controlled by Kerimov. The firms, it said in a statement, are purchasing 63.2 percent of Uralkali. A fourth company controlled by Kerimov, Syona Management, submitted a request for permission to manage Uralkali's business.

The news caused a stir among investors, sending Uralkali's London-traded depositary receipts up 0.5 percent, although they eventually closed down 2.6 percent. If Kerimov were to buy the entire stake, he would need to make a buyout offer to minority owners.

"There was a tragic mistake," said a spokesperson for Kerimov's Nafta-Moskva holding company.

The firm had not planned to send the request, the spokesperson said. A lawyer accidentally sent the document to the anti-monopoly service.

According to the request, a copy of which was obtained by Vedomosti, Kaliha Finance, Aerellia Investments and Becounioco Holdings are not affiliated, although they were seeking to purchase 63.2 percent of Uralkali. Syona would then seek to buy those companies' shares, it said.

Teimuraz Kharitonashvili, head of the anti-monopoly service's chemicals and agriculture department, said the documents identified Kerimov as a beneficial owner of Kaliha Finance and Syona Management. The owners of Aerellia and Becounioco were not identified.

A request would need to have been filed for a deal between Rybolovlev and a tandem of Kerimov and billionaire Mikhail Prokhorov, who had been planning to buy Rybolovlev's entire stake, said a source close to Nafta-Moskva. After Prokhorov decided not to participate, Nafta-Moskva had to seek other partners to split the risks and avoid a minority buyout.

The source told Vedomosti that the new deal was prepared very quickly, which is why companies that ultimately bought Uralkali shares were mistakenly included in the anti-monopoly request. Nafta-Moskva is not planning to raise its stake in Uralkali, the source said.

"All of the current owners of major stakes in Uralkali are strategic partners for Nafta-Moskva," added the source close to the company.

Spokespeople for Nesis and Galchev did not answer questions sent by Vedomosti.