Alexey Ulyukaev is under the investigation for allegedly having received $2 million that led to a positive conclusion, allowing Rosneft oil company to buy Bashneft, the Russian Investigative Committee said early Tuesday in a statement.

The prime minister is informed of Ulyukayev's detention," the cabinet's press service said. "The prime minister discussed the incident with the Russian president."

"The prime minister believes that it is necessary to conduct the most thorough investigation of the case," the cabinet stressed.

According to Kremlin spokesman Dmitry Peskov, Russian President Vladimir Putin was aware of the situation since the launch of the investigation.

"Of course, the president was reported of the issue. He is aware. He was reported, in fact, when the investigation was launched. It means he received all the information. But, I repeat, as I said, these are very serious allegations. And a verdict regarding the consistency of these charges can only be rendered by a court," Peskov stated.

The spokesman added that he is not aware if the Bashneft sale deal will be revised. Rosneft and Bashneft oil and gas companies, the ALROSA group of diamond mining companies, VTB bank, as well as the Sovcomflot maritime petroleum and liquefied gas shipping company, are among the companies to be partially privatized. Russia is due to sell 19.5 percent of Rosneft shares before the end of the year.