THQ have announced that a co-operative “Exterminatus” mode for Space Marine is now available on Steam and PS3. The add-on comes free in a small game update that players will be asked to download next time they sign in to Steam or the PSN. While not yet available for the Xbox 360 version, it is promised that the procedure will be the same.

Once this update is downloaded, you should notice Exterminatus in the menu system. Exterminatus pits you and up to three other space marines against hordes of alien enemies in a score based fight to the death, complete with leaderboards, challenges and score modifiers. You can choose between the Tactical, Devastator and Assault marines, and have access to any perks and weaponry normally available to those classes.

“We are delighted to be able to reward the loyal fans of Space Marine with a new free mode to extend and enhance their game play experience,” says Jim Huntley, Vice President of Global Brand Management.

“Exterminatus will provide a rewarding new challenge to players old and new.”

There are two scenarios available: “Assault on Hab Center Andreas” and “Escape From Kalkys Facility”.

Exterminatus mode is available now on PlayStation 3 and Steam, and will be releasing “soon” on Xbox 360.