Vindictus, Dungeon Fighter Online and Combat Arms coming to Valve's Steam service.

Nexon America is bringing three of its free-to-play video games – Vindictus, Combat Arms and Dungeon Fighter Online – to Steam this month, the company announced today. The additions are part of the growing presence of free-to-play games on Valve's digital distribution service, which now boasts more than 30 titles.

Vindictus, Nexon's "real-physics-based" massively multiplayer online game role-playing game, will be the first title from the publisher to come to Steam. First-person shooter Combat Arms and multiplayer beat 'em up Dungeon Fighter Online are expected later this month.

Valve opened the door to free-to-play games via Steam in mid-2011, releasing its own first-person shooter Team Fortress 2 for free. The service now includes free-to-play games DC Universe Online, Super Monday Night Combat, Everquest 2, The Lord of the Rings Online, Microsoft Flight and many others.

Valve has another free-to-play title in development, Dota 2, which is planned for release sometime in 2012.