A games company is accusing Zynga of infringing its patents and asking that it shut down its most popular games for the Facebook social network, including FarmVille and Mafia Wars.

In a complaint filed on Wednesday in U.S. District Court in Delaware, Agincourt Gaming, which has a Facebook game called Pantheon, claims Zynga infringed two of its patents dating back to 1996 that relate to redeeming virtual prizes in games.

The Texas-company is seeking damages and asking that Zynga shut down 12 games that it says infringe its patents.

Zynga was not immediately available for comment on Wednesday. It filed for an initial public offering of up to $1 billion on July 1.

Zynga is currently in a legal battle with Vostu, a Brazilian games maker. In June, it sued the Brazilian company for allegedly copying its games.

The case is Agincourt Gaming LLC v Zynga Inc, U.S. District Court, Delaware, No. 11-0072O