A games company has accused Zynga of infringing its patents relating to social network gaming.
Agincourt Gaming claims that the maker of FarmVille and Mafia Wars, popular games on the Facebook social network, has infringed two of its patents dating back to 1996 that relate to redeeming virtual prizes in games.
Agincourt Gaming, which has a Facebook game called Pantheon, is seeking damages and asking that Zynga shut down 12 games that it says infringe its patents.
Zynga, which has filed for an initial public offering of up to $1 billion, is currently in a legal battle with Brazilian games maker Vostu, which it says allegedly copied its games.
Zynga was not immediately available for comment.