FacebookDigital Sky Technologies, a Russian Internet-investment group, has offered to invest $200 million in Facebook, the WSJ is reporting, and which our own sources close to the company have since said is “accurate.” However, the company itself has declined to comment.

The offer was for preferred stock and values Facebook at $10 billion. It’s not clear whether the deal will go through. While Facebook has consistently said it doesn’t need extra cash for now, the $10 billion valuation is a solid one, and so Facebook is likely to take it seriously. While Microsoft was reported to have offered a $15 billion valuation when it invested two years ago, many believe that value was too high.

As part of the deal, DST is also offering to buy between $100 million and $150 million in Facebook common stock (the stock owned by the company’s employees) at a $6.5 billion valuation. This is consistent with our own report last week, which said Facebook was raising about $150 million in order to buy stock held by employees who have now worked there for several years and who are eager to cash in on their stock value.

However, if this offer is taken, it lets Facebook’s existing investors (Accel, Greylock, and Founders Fund among others) off the hook from having to participate. We’re told these backers wouldn’t participate if DST’s offer is accepted.

DST, run by Russian Internet investor Yuri Milner, owns part of Russia’s largest Web site, Mail.ru.