Obopay Inc. is expanding its person-to-person money transfer service into gaming.

The Redwood City, Calif., company said Wednesday that people who want to make purchases within online game systems can enroll their Obopay accounts to facilitate the transactions without leaving the gaming sites. The service is also available on the social networking Web site operated by Facebook Inc.

Obopay said that the Web sites could generate more sales if users can make purchases through their sites instead of being redirected to other online merchants to facilitate the transaction.

"The growth of the online game industry shows tremendous promise and is impacting the development and monetization of social networks," Carol Realini, Obopay's founder and chief executive, said in a press release.

Obopay operates a network the lets users send each other money through their mobile phones; the funds are stored in prepaid accounts. The company is also working with Citigroup Inc. and MasterCard Inc. to connect the service to users' primary bank accounts.