It did not specify when it bought the shares or what stake it had acquired in the firm, which has previously raised more than $5 billion in several financing rounds.

"We believe that Uber's highly talented management team possesses the necessary vision and skills to build the company into one of the world's preeminent technology businesses," Fridman, who is the chairman of LetterOne, said.

In January, Russian media reported that another Russian tycoon, Alisher Usmanov, had invested several tens of millions of dollars in Uber in the summer of 2015.

(Reporting by Maria Kiselyova; Editing by Alexander Winning)