James Hill for The New York Times

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MOSCOW — What do the Russians want from Facebook?

And what, for that matter do they want from other hot, and currently private, American companies like Zynga, Groupon and Twitter?

For people with money in the Russian investment company DST Global, the focus is social networking.

The private company, which is generally known here as DST, may seem but a footnote in the move by Goldman Sachs to invest $450 million in Facebook.

But DST’s additional $50 million now raises it and its sister company’s combined investment in Facebook to more than $500 million. As a result of their earlier investments, they now own about 10 percent of the company, making the DST siblings among Facebook’s biggest owners.

When DST, previously known as Digital Sky Technologies, first started putting money into Facebook in 2009, some analysts chalked it up to an effort by novice Russian investors to burnish their technology credentials and gain entree to Silicon Valley. But DST, which is bankrolled by a coal and steel mogul with Kremlin ties, has placed some ambitious, and so far successful, bets.

It now owns about 5 percent of the popular online gaming company Zynga and about 5 percent of the prominent shopping-coupon company Groupon. And it is said to be interested in investing in another privately held phenomenon, Twitter.

A DST representative did not answer phone calls about the deal on Monday, which was a holiday in Russia.

But DST’s chief executive, Yuri Milner, has said his focus on social networking reflects insights gained from watching the Russian Internet market develop in the last few years. In 2005, DST began investing in Internet companies in Russia and Eastern Europe, where, as in parts of Asia, people adopted social games and the trading of virtual goods faster than in the United States.

This, Mr. Milner, has said, led to an understanding that social networking business models involving tiny payments from large numbers of users have vast potential in emerging markets.

“We chose a strategy of total and unconditional focus on the consumer Internet, and I would say, even the social Internet,” Mr. Milner said, according to an interview published Dec. 28, before the Goldman Sachs deal became public, in the Russian business newspaper Vedomosti.

“Global investors with this level of focus, it turns out, are few,” he said. “People usually think more broadly, and then have to follow a large number of sectors and process lots of information.”

But the approach meant that Mr. Milner needed to engage in some social networking of his own — in Russia’s business world.

He linked up with Alisher B. Usmanov, the owner of a Ural Mountain coal and iron ore business and a member of a tight coterie of insider businessmen in Russia known as the oligarchs.

“Thanks to a common acquaintance, I contacted Alisher,” Mr. Milner said in the Vedomosti interview. Despite his brick-and-mortar businesses, Mr. Usmanov keeps a keen eye on Internet developments, Mr. Milner said.

The pairing of Mr. Usmanov’s finances and Mr. Milner’s strategic bets on the direction of the Web form the core of the company, though DST says it is now also reinvesting proceeds from its earlier successes.

One of those was the public offering of Mail.ru, a Russian-language e-mail service and collection of Web properties, on the London Stock Exchange in November that raised more than $900 million.

As a result of that public offering, Mail.ru now owns about 2.4 percent of Facebook, while the still-private DST Global owns about 7.6 percent.

Responding in the past to questions about Mr. Usmanov and his role at DST, Mr. Milner has said that he and his partner owned 40 percent of the firm and made all of its management decisions.

In the Vedomosti interview, Mr. Milner had only praise for the business skills of Facebook’s 26-year-old co-founder, Mark Zuckerberg, saying he “continues to impress with the dynamism of his development as a personality.”

DST’s interest in the increasingly hot private market for shares in social networking sites comes as the Securities and Exchange Commission has opened an inquiry into such trading.

And while it remains to be seen whether the Russian involvement will raise any questions for S.E.C. investigators, there is no question that the Russians and their American investment targets come from vastly different business cultures.

Mr. Usmanov earned his billions in the post-Soviet business world, managing steel mill subsidiaries for Gazprom before they were spun off as his own businesses.

Dating from his work with Gazprom, he is said to be close to President Dmitri A. Medvedev, a former chairman of the Gazprom board.

A native of Uzbekistan, Mr. Usmanov spent six years in an Uzbek prison on a conviction of fraud and embezzlement in the 1980s, charges he contends were politically inspired. A Soviet court later dismissed them, and expunged his record.

The year Mr. Usmanov was doing time in that prison — 1984 — was the year that Mr. Zuckerberg was born.