Mail.ru, a Russian Internet group formerly known as Digital Sky Technologies (DST) and a small stakeholder in Facebook, said Monday it is is planning an initial public offering on the London Stock Exchange by the end of the year. The group, which could be valued at around $5 billion, says its IPO may be valued between $500 million and $750 million.

Though Mail.ru has not yet confirmed any details of the future IPO, a near 15% stake of the company may be sold.

Anybody interested in grabbing a piece of Facebook--no matter how minute--should take heed.

Nearly a year-and-a-half ago, DST invested $200 million in Facebook in exchange for a 1.96% stake of the company at a $10 billion valuation. Mail.ru now commands a 2.4% share of Facebook, a 5.1% share of deal-of-the-day site Groupon, and a 1.5% share of social gaming giant Zynga.

Unfortunately, there won’t be any Facebook share grabbing at this stage. DST will withhold the DST Global name from the IPO and that’s the one that oversees the firm’s investments in Facebook, Groupon, Zynga, and other companies mostly in Eastern Europe.

Facebook executives (including CEO Mark Zuckerberg) and investors (like Peter Thiel) have repeatedly made clear that the company has no plans go public until 2012 at the very earliest.

One of the largest and oldest Russian email websites, Mail.ru also owns ICQ (which DST bought from AOL for $187.5 million in April) and Russian social network Odnoklassniki, as well as shares in another Eastern European social network, VKontakte, and payments platform Qiwi.

Russian billionaire Alisher Usmanov, Chinese online service provider Tencent Holdings Ltd., and Goldman Sachs Group Inc. count themselves among Mail.ru’s current shareholders.