Liberty Digital, the tech investment arm of Liberty Media Group, said Thursday it has invested in UGO (Unified Gamers Online) Networks, an online entertainment site targeted at men 18-34.

Liberty Digital made the investment as part of UGO’s fourth round of financing.

Financial terms of the multimillion-dollar deal were not disclosed, but Liberty becomes the largest investor in the New York-based Web site that provides news and info on music, games, film, TV, animation, extreme sports and technology.

Liberty Digital, which is developing interactive television programming for distribution over the Internet and other digital platforms, may use the site to develop content. The site “offers a potentially tremendous opportunity for our interactive television programming services,” said Liberty Digital prexy and CEO Lee Masters.

UGO attracts more than 4 million visitors monthly.

“Liberty Digital’s weighty investment in UGO clearly demonstrates its confidence in our continuing dynamic growth,” said UGO Networks chairman Joe Robinson. “The investment provides UGO with a strong capital base to further our expansion as the dominant force in the 18- to 34-year-old male market.”

Liberty Digital already holds stakes in Interactive Pictures Corp. (IPIX), TiVo, Drugstore.com, iVillage.com, Priceline.com, Quokka.com and Sportsline USA.

In September, Liberty Media formed Liberty Digital and transferred its Web assets to the new company.