Russian investment firm Digital Sky Technologies has begun buying more shares in Facebook, seeking to expand its stake in the world's No. 1 social networking company, two sources told Reuters.

DST has begun purchasing shares directly from Facebook shareholders, two people familiar with the deal said on Thursday on condition of anonymity.

Their appetite with me is: 'whatever you have, we'll take it,' said one of the sources, a Facebook shareholder who agreed to sell his stock.

According to the shareholder, DST is offering $14.77 a share, the same price paid in July when it bought $100 million of Facebook shares from the social networking site's employees and ex-employees, at a $6.5 billion valuation. [ID:

DST also invested $200 million in Facebook preferred shares in May. The two transactions gave DST a 3.5 percent stake in the company.

A second source familiar with the matter said DST could buy up to $100 million of additional Facebook shares, though that amount had not been finalized.

Representatives for Facebook and DST were not immediately available for comment.

(Reporting by Alexei Oreskovic)