A group of gamers is suing to stop Microsoft from buying video game publisher Activision Blizzard, arguing that the $68.7 billion acquisition would stifle competition and reduce consumer choice.

The lawsuit was filed late Tuesday in a U.S. federal court in San Francisco on behalf of 10 individual gamers who are fans of Activision Blizzard's Call of Duty franchise and other popular titles such as World of Warcraft, Overwatch and Diablo.

Microsoft is facing a number of legal challenges as it tries to finalize what would be the priciest-ever merger of technology companies. The Federal Trade Commission earlier this month sued to block the takeover, saying it could suppress competitors to Microsoft’s Xbox game console and its growing games subscription business. Antitrust regulators in the United Kingdom and European Union are also investigating the deal.

Several of the plaintiffs in the private antitrust lawsuit said they play Activision Blizzard games on Sony’s PlayStation, the main rival to Microsoft’s Xbox. Others said they play them on personal computers, Xbox or Nintendo's Switch.

In response to the lawsuit, Microsoft said Wednesday that the merger “will expand competition and create more opportunities for gamers and game developers as we seek to bring more games to more people.”